Abstracts of Papers Communicated to the Royal Society of London Source: Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, Vol. 167, No. 931 (Sep. 23, 1938), pp. S97-S112 Published by: The Royal Society Stable URL: http://www.jstor.org/stable/97202 . Accessed: 08/05/2014 09:30 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. . The Royal Society is collaborating with JSTOR to digitize, preserve and extend access to Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences. http://www.jstor.org This content downloaded from 169.229.32.137 on Thu, 8 May 2014 09:30:07 AM All use subject to JSTOR Terms and Conditions
Transcript
Abstracts of Papers Communicated to the Royal Society of LondonSource: Proceedings of the Royal Society of London. Series A, Mathematical and PhysicalSciences, Vol. 167, No. 931 (Sep. 23, 1938), pp. S97-S112Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/97202 .
Accessed: 08/05/2014 09:30
Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp
.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].
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OF PAPERS COMMUNICATED TO THE ROYAL SOCIETY OF LONDON In accordance with a resolution of Council, summaries or abstracts of papers are to be published as soon as practicable. The publica- tion of such abstracts in no way indicates that the papers have been accepted for publication in any fuller form. These abstracts will be issued for convenience with the "Proceedings of ,the Royal Society of London" but do not form a -part of the "Proceedings "
6 SEPTEMBER 1938
The effects of thunderstorms and lightning discharges on the earth's electric field. By T. W. WoRMELL. (Communicated by C. T. B. Wilson, F.R.S.-Received 29 June 1938.)
The results of an extended series of observations of the potential gradient during thunderstorms in the years 1926-36 are discussed. A capillary electrometer was used to record photographicallythe behaviour of the gradient, and continuous observations were possible even in the most intense fields and' throughout heavy rainfall. The effects of lightning discharges could be detected up to about 40 km. distance. The time of response of the recording system to a sudden change in the field was about 005 sec. and the method thus yields an accurate record of the behaviour of the pre- discharge gradient, of the recovery of the field after a discharge and also a certain amount of detail during the change of field accompanying a discharge.
Records of a number of storms are reproduced and discussed in detail. The values of the pre-discharge gradient beneath a thundercloud rarely exceeded
10,000 V//m. even just before a close lightning flash. Negative gradients were on the average more intense than positive ones at all distances from the storm. When dis- charges were occurring within 5 km., negative pre-discharge gradient was twice as frequent as positive; beyond 10 km., positive gradient predominated.
'The magnitude of the field changes due to very close discharges was very variable. The biggest observed, of either sign, exceeded 50,000 V/m., but flashes within 1 km. occasionally caused changes of only a few thousand volts per metre.
The magnitude of the field changes at greater distances leads to an estimate of the electric moment of the discharges. The mean value deduced for this quantity (i.e. twice the product of the charge by its vertical displacement) was, about 220 coulombs x kilometres. The values for positive and negative discharges were not greatly
different.
Abstracts [ S 97 1 13
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The most distant discharges recorded showed an excess of negative field changes (i.e. of changes tending to reduce the value of a positive potential gradient). For discharges within 15 km. there was a considerable excess of positive field changes, the proportion increasing with decreasing distance until at about 5 km. distance positive changes were more than three times as frequent as negative ones. This well-known behaviour is commonly interpreted as due to the frequent occurrence of a discharge involving the main positive charge at the top and negative charge in the, base of the thundercloud. For the very close discharges there was however, in the present series of storms, a marked increase in the proportion of negative field changes, positive and negative changes being about equally frequent for discharges within 3 km. The observations'would seem to demand the not infrequent occurrence of a second type of cloud discharge which causes a negative field change at short distances, but a positive change beyond its small reversal distance, and must be very low down.
About one quarter of all the field changes recorded, even with this rather slow apparatus, showed components of both signs. For very close discharges the propor- tion was considerably higher. Such complex field changes were sometimes observed when only a single flash, either in the cloud or to earth, was visible in daylight. Many of the simple field changes showed appreciable duration on the records, in a few cases exceeding 05 sec. In some cases this was clearly due to the discharge being made up of several strokes but in others the change was recorded as a slow smooth variation of the field.
The form of the recovery of the field after a discharge is discussed in detail and it is concluded that the initial rate of regeneration of electric moment by the cloud is, on the average, about 0*15 of the moment destroyed by the flash per second.
A brief discussion is given of our present knowledge of some of the fundamental quantities connected with a thundercloud and of the theory of the mechanism of the production of the charges.
The use of a vertical pipe as an overflow for a large tank. By A. M. BINNIE. (Communicated by R. V. Southwell, F.R.S.-Received 30 June 1938.)
The performance of vertical pipes arranged as overflows in a tank was studied experimentally on a small scale with special apparatus, which ensured that the water reached the pipe inlet with no tangential component of velocity.
Under niormal conditions the change of head with discharge was small at low heads. At this stage the flow was not rotational, but a considerable volume of air was drawn down the pipe in the form of bubbles. Above a sharply marked critical head, the pipe ran full and a large rise of head caused only a slight increase in the discharge. The effects on.the critical head of lengthening the pipe and of sharpening its inlet end were comparatively small, but the insertion of a trumpet-shaped mouthpiece greatly improved the performance.
The types of flow described by Borda as free and full flow were possible with over- flow pipes of uniform diameter, and they resulted in a serious reduction in the dis- charge.
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The electromagnetic energy of a point charge. By M. H. L. PRYCE. (Corn- municcted by P. A. M. Dirc,c F.R.S.-Received 30 June 1938.)
A method of defining the energy of a point charge in a finite manner is developed. It is roughly equivalent to subtract'mg an infinite constant from the ordinary expres- sion in an unambiguous and relativistically invariant way. The energy and momen- tuum are quite simply given as the sum of a mechanical part and a (convergent) integral over all space. For a point charge in uniform motion the energy and momen- tum are the same as for a particle possessing inertia.
The equations of motion for a point charge are derived from the conservation of energy and momentum.
In ? 5 the theory is presented symmetrically with regard to the advanced and retarded fields.
An absolute determination of the acceleration due to gravity at the National Physical Laboratory. By J. S. CLARK. (Communicated by W. L. Bragg F.R.S.-Received 5 July 1938.)
An absolute determination of the value of g at the N.P.L. has been carried out, using a reversible pendulum swinging in vacuo on a fixed knife-edge, the plane- bearing surface being part of the pendulum itself.
The pendulum was designed to be as rigid as possible, and special attention was given to the calculation of the correction due to the elastic deformation of the pendulum when oscillating.
Investigations were also made to determine the corrections due to curvature of the knife-edges, elasticity of -the support, amplitude of swing, and the residual pressure.
The mean result of eighteen determinations gave the value of g at the N.P.L. (lat. 510 25' 14' N., long. 00 20' 21' W., and height above M.S.L. lOnm.) as 981-1815 cm./sec.2
Specific heat-temperature curves of some age-hardening alloys. By N. SWINDELLS and, C. SYKES. (Communicated by W. L. Bragg, F.B.S.- Received 5 July 1938.)
The changes in atomic configuration taking place during hardening affect the apparent specific heat of age-hardening alloys. Specific heat-temperature curves and hardness measurements have been obtained on five typical age-hardening alloys.
The results show that in certain cases, e.g. the silver-copper and copper-beryllium alloys, maximum hardness is attained when the major portion of the chemical energy associated with the supersaturated solid solution has been evolved, i.e. precipitation has taken place. In other cases, duralumin and aluminium-copper alloys, maximum hardness is associated with segregation of the solute atoms in the parent lattice prior to precipitation.
I3-2
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The classical equation of state of gaseous helium, neon and argon. By R. A. BITCKINGHEAM. (Communicated by J. SE. Lennard-Jones, F.R.S.- Received 11 July 1938.)
The problem of deriving the form of the interaction of rare gas atoms from their observed second virial coefficients is attacked by the method introduced by Lennard- Jones, using the classical equation of state and for the interaction energy
E(r) =Ar-s - Ir-t. (1)
The method of calculation ed by Lennard-Jones for helium, neon and argon, assuming A and it constant, has been modified and then extended to allow for a possible slow variation ofA with r. The bearing of the results upon the true interaction of helium atoms is discussed, mainly in relation to the accuracy of the Slater field. For neon and argon it is emphasized that an unambiguous determination of the interaction energy requires an accurate knowledge of the properties of the crystalline form of these elements. The description of the repulsive potential by analytic expressions, such as be-rlP and b1r7e-rIP, is considered,- and. parameters deduced which give the best correlation of gas and crystal data, on the assumption that (1) and kindred forms are valid for the interaction of neighbouring atoms only in the crystals.
The formation of negative ions by positive-ion impact on surfaces. By R. PRESS and R. H. SLOANE. (Communicated by E. V. Appleton, P.R.S. -Received 12 July 1938.)
It has been found that when a hot-cathode discharge is passed through mercury vapour, light negative ion are produced from surfaces exposed to- positive-ion bombardment. The negative ions include some with energies greater than could be imparted to them in the existing electric fields. Experiments are described which eliminate the possibility that the excess energies could be produced through electrical oscillations. The conditions under which the negative ions appear indicate that they are produced mainly through sputtering of occluded electronegative films under the action of mercury positive-ionbombardment, but results from experiments of this type cannot be interpreted unambiguously. The existence of this process has been shown directly by a double mass spectrograph in which beams of positive ions of known kind are allowed to impinge normally on a metal disk in high vacuum and are found to produce a spectrum of negative ions, with properties similar to those of the negative ions obtained in the previous experiments. The existence of Hg- as a stable entity seems to be still in doubt.
The porous diaphragm method of measuring diffusion velocity, and the velocity of diffusion of potassium chloride in water. By G. S. HARTLEY
and D. F. RUNNICLES. (Communicated by F. G. Donnan, F.R.S.-Received
12 July 1938.)
A continuous reading apparatus for measuring the rates of diffusion of pure electrolytes through porous diaphragms is described.
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Results obtained for the diffusion of potassium chloride as a function of concentra- tion are presented and the absolute values obtained by extrapolation.
The comparison of the results obtained with the best available data by absolute measurements shows that there is still room for more accurate work in the whole problem, but it is believed that the diffusion coefficients in the range from N/100 to N/1O are accurate to within 2 %.
The determination of the size of paraffin-chain salt micelles from diffusion measurements. By G. S. HARTLEY and D. F. RUNNICLES. (Communicated by F. G. Donnan, F.R.S.-Received 12 July 1938.)
The porous diaphragm method has been applied to the measurement of the diffusion of paraffin-chain micelles in aqueous solution with a swamping excess of simple electrolyte.
For cetyl pyridinium salts the method is satisfactory and a radius for the micelle of about 26 A is found. The radius is independent, within experimental error, of the concentration of paraffin-chain or swamping electrolyte, and very little dependent on temperature. These results are in excellent agreement with the "spherical liquid micelle " theory. There is small, but definite, influence of the nature of the gegenion on the size of the micelle.
For cetane sulphonates and cetyl sulphates the method fails to give reliable results, probably owing to the building up of a structure within the pores of the diaphragm.
When the solutions are saturated with amyl alcohol or benzene the method again fails to give reliable results. A mechanism is suggested for the anomalies observed.
The simultaneous sorption of carbon bisulphide and water vapour by activated charcoals. By A. J. ALLMAND, F.R.S. and J. L. Lizius. (Received 12 July 1938.)
Although accurate work has recently been published in the Proceedings on the adsorption of gaseous mixtures on solid sorbents, the authors do not think that similar work of any value has appeared dealing with the simultaneous adsorption of two vapours. They have attempted to carry out such measurements, using water 'and carbon bisulphide as the sorbates, and three activated charcoals of varying character as the sorbents. The technique employed, including pressure measurements by means of a Pirani gauge, was an extension of that already described in the Proceedings of the Society.
Experiments were carried out on the effect of varying charges of water vapour on the pressure exerted by a constant charge of carbon bisulphide sorbed on charcoal, on the sorption isothermals of water on charcoal containing such a charge of carbon bisulphide, and also on the sorption isothermals of carbon bisulphide on charcoal containing a constant charge of water. The results are expressed in the form of diagrams. They are of some complexity, due to the complications involved in the use of water vapour.
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The discussion is a somewhat detailed one, necessarily so in the opinion of the authors, in view of the complex nature of the systems studied. It commences with a resume of our present knowledge of the nature of the sorption of water and carbon bisulphide vapours by the charcoals of the particular types used-points to a paral- lelism between certain results in the present paper and the sorption isothermals of water on charcoal-makes detailed suggestions regarding the nature of the different stages of the latter (adsorption of single molecules passing gradually over to the formation of a continuous adsorbed film, with irreversible capillary condensation superposed)-explains the effect of an increasing water charge on the pressure of a constant carbon bisulphide charge in the light of these suggestions-shows how the isothermals of carbon bisulphide on charcoals containing sorbed water are consistent with the same views.
The mammary gland of the rhesus monkey under normal and experi- mental conditions. By S. J. FOLLEY, A. N. GTUTHKELCH and S. ZUCKERMAN. (Communicated by W. E. Le Gros Clark, FR.S.-Received 13 July 1938.)
Examination of the mean mammary gland area of twenty-six non-pregnant normal female rhesus monkeys shows that over the body-weight range 3400-6060 g. the gland grows according to the simple allometric law. The first menstrual cycles of the rhesus monkey after puberty are usually anovular. Until ovulation occurs, mammary glands grow by proliferation of their ducts, and alveoli do not appear to form until after luteinization has occurred.
Normally the mammary gland of the male rhesus monkey consists of a relatively uncomplicated duct system which does not extend far beyond the base of the nipple. One otherwise normal male showed a condition of gynaecomastia, with clumps of fully formed alveoli. Thirteen male monkeys were injected daily with varying quantities of oestrone for periods ranging from 6 to 484 days. Only one of these animals (one that was injected for fewer than 15 days) failed to show duct prolifera- tion. Only one showed alveolar formation, no alveoli being present in the two animals which received the longest treatment (368 and 484 days respectively).
Only two of four female rhesus monkeys which were spayed before the beginning of the treatment with oestrone (37-365 days) showed alveolar formation. Testosterone propionate appears to stimulate stunted duct development and alveolar formation in male monkeys.
No carcinomatous changes were observed in the mammary glands of any of six monkeys which were injected daily with oestrone either continuously or for the major part of periods varying between 365 and 938 days.
The thermal decomposition of nitrous oxide. By C. N. HINSHELWOOD, F.R.S. and R. M. LEWIS. (Received 15 July 1938.)
Further experimental data relating to the thermal decomposition of nitrous oxide at 7470 and 6520 are recorded.
The variation of reaction rate with pressure is expressed both in terms of the reciprocal half time of reaction and in terms of the initial rates. The two curves
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obtained are similar enough to show that previous conclusions based upon the half- time curves are confirmed by the initial rate curve.
The mean value of the activation energy falls at lower pressures, and the absolute magnitude of this energy agrees with most previous determinations, but not with those upon which has been based a theory that the reaction is abnormally slow for certain quantum mechanical reasons.
The influence of the products of reaction and of additions of nitrogen, argon and carbon dioxide has been studied. There is a contrast between the action of argon and that of carbon dioxide in that the former has a relatively greater effect at lower than at higher partial pressures of nitrous oxide. This fact is consistent with a greater complexity of the reaction mechanism than corresponds to the assumption of a single "4quasi-unimolecular" reaction. The nature of this complexity is discussed.
On the stability 'of flow between parallel planes. By D. MEKSYN. (Communicated by L. Bairstow, F.R.S.-Received 20 July 1938.)
The equations of motion of a viscous fluid for the case of flow between two parallel planes are considered, and it is shown that at sufficiently high Reynolds numbers and sufficiently small wave-lengths, neutral vibrations of small amplitude can coexist with a laminar flow. For moderately large values of R neutral vibrations can exist only for discrete values of R and A, the wave-length of the vibrations.
The band spectrum of silicon monosulphide and its relation to the band spectra of similar molecules. By R. F. BARROW and W. JEVONS. (Communicated by A. Fowler, F.R.S.-Received 21 July 1938.)
The spectrum of SiS is investigated in emission by heavy-current discharges through a mixture of SiS vapour and argon. In the region A2585-3959 is a system of some 70-80 red-degraded bands with single heads:
(where u = b + 1). That the lower state is the ground state of SiS is proved by the fact that some of the band heads (with v" = 0 and 1) have been measured in absorp- tion by SiS vapour. In the region A3491-6169 in the SiS discharge are about 70-S80 red-degraded bands, which form a part of a second extensive system, probably of SiS, with neither state in common with the first. The vibrational frequencies for the upper and lower states are of the same orders for the two systems. The first system alnost certainly involves singlet states (either 1E :Z? x'E or 1I1:T : x'E), while the second system, which resembles the 32 :E: 3a system of S2 in appearance, may involve triplet states of SiS. The first system occurs also in heavy-current discharges through A12S3 vapour and argon, and through BC13 vapour and H2S, in silica tubes, apparently without the second system. The energies of dissociation of SiS in the ground state and excited state of the first system are about 6 0 + 0 3 and 2 1 + 0 5 eV respectively,
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and the products of dissociation are probably unexcited atoms, Si(3P.) + S(3P) in each case. The numerical constants for the ground states and certain excited states of the diatomic oxides, sulphides and selenides of group IV (B) atoms are surveyed, and from the empirical relations described the constants for the expected systems of SiSe and GeSe are estimated.
The behaviour of polar molecules in solid paraffin wax. By R. W. SILLARS. (Communicated by E. V. Appleton, FR.S.-Received 25 July 1938.)
The experiments described constitute an extension of previous work by Jackson and were carried out on solid samples of paraffin wax containing small concentrations of various long-chain esters. The esters are of molecular type similar to the wax, but have a permanent electric moment in virtue of the ester group. Dipole effects similar to those found by Jackson are observed, and the variations of the characteristic time constants with temperature and with chain length of the esters are studied. Variation with temperature is approximately exponential, the exponent being about the same for each ester. It is found that the time constant is a non-linear function of the total chain length of the ester molecule, but is relatively independent of the position of the ester group in the chain. It is confirmed that the observed losses are due to dipole effects and not to some adventitious cause. It is concluded that the whole ester molecule contributes to the time constant, and therefore that it behaves as a rigid structure and does not simply become deformed in the immediate neighbourhood of the dipole group. This is in agreement with evidence from other sources. The results do not suggest any simple relation between chain length and time constant, and a satisfactory theory to relate them has yet to be found.
The specific heat of 4-brass. By R. EISENSCHNITZ. (Communi cated by Sir William Bragg, F.R.S.-Received 26 July 1938.)
A theoretical investigation is made of the specific heat of ,-brass. The following assumptions are made in the course of the calculation: The interaction energies of the atoms vary with the square of change of volume; the energy minimum of the average of Cu-Cu and Zn-Zn energies lying at higher volume than the minimum of Cu-Zn.
The partition function at constantSvolume is calculated according to the theory of Bragg and Williams; the corresponding partition function at constant pressure is obtained by taking an average over the variable volume.
It is shown that the specific heat curve can be adjusted so as to give good agreement with experiment for temperatures below the maximum of specific heat.
The theory of Bragg and Williams is applied to a lattice containing a finite number of atoms. By introducing this number, agreement is obtained with the experimental slope of the C, curve beyond the maximum. A theoretical estimate is made which justifies the introduction of this finite number.
A general theorem of statistical mechanics is derived, according to which all thermodynamical quantities in physically realizable systems are analytic functions of the temperature.
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The effect of solvents on the continuous absorption spectrum of bromine. By R. G. AiCKIN, N. S. BAYLISS and A. L. G. REES. (Communicated by F. G. Donnan, F.R.S.-Received 26 July 1938.)
The visible and ultra-violet absorption spectrum of bromine has been investigated in the following solvents: water (2N sulphuric acid), cyclohexane, chloroform, carbon tetrachloride, benzene, chlorobenzene, toluene.
The weak ultra-violet absorption of gaseous bromine is enormously enhanced in solution, particularly by the aromatic solvents. The smallest effect occurs in carbon tetrachloride, where considerable deviations from Beer's law were found. Absorption maxima in the ultra-violet were found at 2500 A in cyclohexane, at 2725 A in chloro- form, and in the neighbourhood of 2950 A in the aromatic solvents.
In the region of the visible continuum, the non-aqueous solvents cause a marked increase in absorption intensity combined with a small or zero shift of the maximum towards the ultra-violet. Water causes a large displacement (1750 cm.-') of the maximum to higher frequencies; but only a very small increase in intensity. If the A component of the visible continuulm is complex, the displacement of the maximum in non-aqueous solvents can be interpreted as due to a greater solvent effect on 1 *- e 1. than on 3H-+ 217+. The transition 3H, 1L is less affected still. Difficulty is found in interpreting the observations if the B continuum is complex and A simpleA
Oscillatory motion of a fluid along a circular tube. By D. G. CHRIS- TOPHERSON, A. GEMANT, A. H. A. HOGG and R. V. SOUTHWELL, F.R.S. (Received 26 July 1938.)
This paper is concerned with oscillatory motion (either free or forced) of a viscous fluid along a circular tube: the restoring force comes in both instances from the "gravity head" which results from the passage of fluid. Part I is a theoretical dis- cussion of the problem. Part II deals from a practical standpoint with complicating factors (e.g. turbulence, or meniscus and other end effects) which the theory does not take into account, and briefly discusses the possible application to viscometry. Part III gives the results of experiments made to test the predictions of Parts I and II.
The surface migration of barium. By M. BENJAMIN and R. 0. JENKINS. (Communicated by R. H. Fowler, F.R.S.-Received 27 July 1938.)
It is found that under similar vacuum conditions barium does not migrate over tungsten, although thorium does. It is also shown that barium does not migrate over nickel.
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The yield of mild steel, with particular reference to the effect of size of specimen. By J. L. M. MORRISON. (CoMMunicated by R. V. Southwell, F.R.S. -Received 28 Jfuly 1938.)
The paper describes an investigation carried out to determine by means of tests under various conditions of uniform and non-uniform stress distribution the criterion of yield in specimens of mild steel.
Apparatus is described for heat-treating material after machining in such a manner as to avoid surface decarburization, and for determining the stresses at yield of specimens tested in tension, compression, flexure, torsion and combined tension and torsion. Experiments are described which indicate that the material used is uniform and isotropic; and the results of certain earlier investigations are compared with those found in the present paper.
No differences are found between the yield of mild steel in tension and compression. The tests in combined tension and torsion give results in accordance with the theory
of yield at a critical value of the shear strain energy stored per unit volume of the material. It is later shown that this result is due to the size of specimen tested.
Tests in tension on solid specimens of varying size and on thin tubes indicate that the character of the yielding of mild steel is a result of the polycrystalline nature of the material.
It is shown that in all cases of non-uniform stress distribution the yielding depends on the size of the specimen. The explanation advanced to account for this result is that in such cases yield is delayed until a shear stress not less than the shear stress at yield under uniform stress is applied to a thickness of material of the order of a few crystal diameters.
The band spectrum of antimony fluoride (SbF). By H. G. HOWELL and G. D. ROCHESTER. (Communicated by W. E. Curtis, F.R.S.-Received 28 July 1938.)
The spectrum of SbF has been produced in active nitrogen and also by means of a high-frequency discharge. It consists of three groups of bands lying in the regions 3600-5000, 2600-2700 and 2200-2430 A. Most of the bands in the first region had already been shown by Rochester to belong to two systems. The remaining bands in this group are here allocated to a third system. As the vibrational constants of these three systems are very nearly the same they are considered to be due to transi- tions between triplet electronic levels. Similarly, the ultra-violet bands form a triplet system, one component being in the region 2600-2700 A and the other two between 2200 and 2430 A. The final state is common to both triplet systems and is probably 3H. The multiplet separations of the states is not known nor is the nature of the other electronic levels.
The vibrational constants of all the SbF systems are as follows:
The comparative behaviour of mammalian eggs in vivo and in vitro. II. The development of fertilized and artificially activated rabbit eggs. By G. PINCUS. (Communicated by J. Hammond, F.R.S.-Received 3 August 1938.)
This paper describes: (i) the sequence of changes occurring between sperm attachment and the first
cleavage division in rabbit ova normally fertilized in vivo; (ii) the cytological changes occurring in unfertilized rabbit ova during their sojourn
in the fallopian tubes; (iii) the cytological behaviour of unfertilized ova subjected to five activating
treatments (exposure to (M) hypertonic solution, (b) supranormal temperatures, (c) treatment with rabbit sperm, (d) treatment with rat sperm, and (e) culturing in a moist chamber) is categorized, and the various events ensuing upon activation are described and discussed;
(iv) the effects of varying the intensity and duration of the hypertonic solution and heat treatments;
(v) the results of treating rabbit ova with the spermatozoa of six species of mammal other than the rat and rabbit;
(vi) a series of transplantations of artificially activated rabbit ova. These experiments are taken to demonstrate that: (1) both ovarian and tubal ova
activated by these treatments in vitro will in varying degrees exhibit development comparable to that of normally fertilized eggs; (2) the initiation of activation is an all-or-none process though its continuation probably is not; (3) haploid, diploid or tetraploid parthenogenesis results from the treatments employed; (4) the intervention of atretic processes may arrest the development of activated eggs at any develop- mental stage; (5) foreign sperm may activate rabbit eggs to a limited degree, but, except in certain instances with rat sperm, the foreign sperm do not penetrate the zona pellucida of the rabbit eggs; (6) living young may arise from artificially activated eggs, but only in a limited number of cases.
The heat of shortening and the dynamic constants of muscle. By A. V. HILL, Sec. R.S. (Received 3 August 1938.)
Further improvements in thermopile and galvanometer systems are described which have made it possible to read the initial heat production directly from photo- graphic records, in absolute units and (for most purposes) without analysis.
When a muscle shortens, in a tetanically maintained contraction, it liberates extra energy in two forms, (i) as "shortening heat", in amount proportional to the shorten-
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ing, and (ii) as external mechanical work. The shortening heat is independent of the load, and therefore of the work done and the speed of shortening. The rate of energy liberation, i.e. of work,+ heat, is a linear function of the load, increasing as the load diminishes.
The " dynamic constants " of muscle, in a maintained contraction, are defined and measured. They are:
a, the shortening heat per cm. of shortening; P0, the isometric tension; b, the increase of energy rate per g. wt. of load.
At any temperature these quantities are very constant: a/P0 is independent of tem- perature, b has a temperature coefficient of about 2t05 per 100C. A "characteristic equation" is deduced for the speed of shortening v under a load P, viz.
(P + ) (v + b) const.
This equation is very accurately obeyed. By fitting it to observations of v and P, the same constants a and b are obtained as are given by heat measurements.
When a contracting muscle is made to lengthen gradually by applying a load rather greater than the isometric 'tension there appears to be a negative heat of lengthening, and the total energy given out by the muscle is less than in an isometric contraction. The energy relations in lengthening are the converse of those in shortening and seem to be governed by the same rules.
The nature of the shortening heat, and the mechanism by which the energy rate is governed by the load are discussed. It is suggested that the chemical processes by which energy is liberated involve certain active points in the molecular machinery, and that when these are occupied in attracting one another and producing a tension they are not available to take part in chemical reaction.
The work done by a muscle in raising a load, or in overcoming an elastic resistance, is transformed into heat in relaxation.
The "visco-elasticity" of contracting muscle is shown to be the property of a two-component system, the one component being undamped and elastic, the other being governed by the characteristic equation (P + a) (v + b) = const., and its corre- sponding energy relations. The fact that an active muscle shortens more slowly under a greater force is due, not to "viscosity" but, as Fenn has claimed, to the manner in which the energy liberation is regulated. A large force causes a low energy rate, which results in a low speed.
From this can be deduced (i) the form of the isometric contraction, (ii) the form of the force-distance curves made, at constant veloeity, by the Levin-Wyman ap- paratus, and (iii) that the greatest rate of doing external work should occur with a load equal to about 30 0 of the isometric tension.
The specific heat of gases at high temperatures. By R. W. FENNING and A. C. WHIFFIN. (CoMmunicated by W L. Bragg F.R.S.-Received 3 August 1938.)
(a) Introductory (reasons for enquiry). At the time this investigation was authorized there was some uncertainty as to the accuracy of the "accepted" values of the molecular heat, at high temperatures, of the gases which comprise the working fluid
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of the internal combustion engine, and in view of the experience that had already been gained at the N.P.L. in connexion with gaseous explosions in closed vessels, it was recommended that a redetermination of this fundamental physical property should be attempted.
(b) Range of investigation. By carrying out explosions of mixtures of the type (2 + a) Co + 02 + bA, and replacing the argon in turn by CO, N2 and CO2' values have been obtained of the mean molecular heat of these gases between 3730K and about 2370, 2650, 2930 and 3060?K. By balancing the heat losses in each group of explosions, the direct measurement of such heat losses was avoided although their magnitude could eventually be obtained from the heat capacity equations.
Determinations have also been made of the mean molecular heats at constant volume of H2 and H20 (gas), the measurements being made from 3730 K to temperatures ranging from about 2100 to 29000K. Although the highest tem- perature is considerably below that attained in the case of CO, N2 and C02, it is believed to be a considerable advance on earlier work, the temperature extension being obtained by the substitution of nitrous oxide for oxygen in the explosive mixtures. The H2 and H20 determinations are dependent on heat loss measurements for which a special device was employed.
(c) Conclusions. The values obtained for the mean molecular heats at constant volume of CO, N2, CO2, H2 and H20 (gas) are represented by the following equations over the specified temperature ranges:
Between 373?K and temperatures ranging from 2350 to 30700K: = 4-854 + 0*037725T -0*07875T2,
CN2 = 4-795 + 0-037675T-0-07875T2,
C02= 8*631 + 0-001522T-0-0615T2.
Between 373?K and temperatures ranging from 2050 to 29300 K:
CH2 = 4*089 + 003953T -0*0798T2,
CH20 = 4*874+0*002284T-0-06256T2,
where T = upper temperature in degrees Centigrade absolute. These values are compared with molecular heats deduced by other investigation
from spectroscopic data and, for the ranges specified above, represented by
A further study of the problem of nuclear isomerism: the application of the method of coincidence counting to the investigation of the y-rays emitted by uranium Z and the radioactive silver Ag106. By J. V. DUNWORTH and N. FEATHER. (Communicated by E. V. Appleton, F.R.S.- Received 3 August 1938.)
The application of the method of coincidence counting by electrical means to the study of the time correlation of nuclear processes-particularly that of successive quantum emission-is discussed in detail. It is shown that a knowledge of the energy dependence of the sensitivity of the counters is essential for any interpretation of the results of such experiments. For the y-ray counters employed in the present investiga- tion some information on this point has been obtained by the use of sources of thorium-active deposit of short and long exposure. In the course of this work the general validity of the ideas of Ellis and Mott (x933) and of the nuclear level schemes of Oppenheimer (I936) has been established. Also the paired quanta of the annihila- tion radiation of positrons have been utilized in the calibration.
A study of the y-radiations from U Z and the long-lived modification of Ag'06 by the coincidence method has shown, in the former case, the emission of two quanta in succession in a very large fraction of the disintegrations, and, in the latter, the emission of four or five quanta in succession in the most probable mode. This result is in general accord with the view that nuclear isomers are to be distinguished one from the other by a small difference in energy content and a large difference in angular momentum. The particle emission from the short- and long-lived modifications of Ag106 has also been studied. It appears probable that the negative electrons of the long-period activity are internal conversion electrons associated with nuclear transitions following K electron capture, rather than that they represent a distinct mode of disintegration of the long-lived radioelement, Ag'06.
Relaxation methods applied to engineering. IV. Problems relating to elastic stability and vibrations. By K. N. E. BRADFIELD, D. G. CHRIS-
TOPHERSON and R. V. SOUTHWELL, F.R.S. (Received 3 August 1938.)
Preceding papers in this series have been concerned with unique solutions: this paper deals with problems such that a complete solution would define an infinite number of configurations, all satisfying the governing equations and the terminal conditions, but each associated with some particular value of a critical loading or frequency (the "characteristic number", or eigenwert). The strut and vibrating rod (of non-uniform section) have been chosen for detailed treatment as the simplest examples, respectively, of elastic stability and vibrations; but the principles as distinct from the details of our "relaxation" treatment are quite general, and they provide a new method of attack on problems which are at once difficult and important.
In both problems the relaxation method appears capable of determining, with more than sufficient accuracy for practical purposes (when dimensions etc. are not known exactly), not only characteristic numbers but also the mode associated with each. (The modes are not determined by the well-known theorem of Lord Rayleigh.)
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The nature of sliding and the analysis of friction. By F. P. BOWDEN and L. LEBEN. (Communicated by C. I. Taylor, F.R.S.-Received 8 August 1938.)
A detailed analysis of the kinetic friction between moving metals shows that the frictional force does not remain constant during sliding. Sliding is not a continuous process: the motion proceeds in jerks, and lairge and violent fluctuations occur in the friction. In the case of dissimilar metals the top surface sticks to the bottom one and moves with it until, as a result of the gradually increasing pull, a sudden and very rapid slip occurs. The process is then repeated indefinitely. A simultaneous measurement of the surface temperature shows that this too is fluctuating and, at the instant of slip, there is a sudden temperature "flash".
The exact behaviour depends upon the relative physical properties of the metals, particularly on the melting point, and there is evidence that three distinct types of sliding may occur. The experiments suggest that friction is due to a welding together of the metals at the local points of contact. These metallic junctions are large com- pared with the dimensions of a molecule and when they are broken the metal is distorted to a considerable depth.
Even if the surfaces are lubricated with mineral oils or other lubricants an inter- mittent clutching and breaking away of the surfaces occurs and the behaviour may be essentially the same. Certain long chain fatty acids may prevent stick-slip and allow continuous sliding to take place.
The area of contact between stationary and between moving surfaces. By F. P. BOWDEN and D. TABOR. (Communicated by G. I. Taylor, F.R.S. Received 8 August 1938.)
An estimate of the real area of contact between stationary and between moving metal surfaces has been made by electrical and by visual means. Experiments with stationary surfaces show that the area of intimate contact is very small. It varies with the pressure, but for flat steel surfaces it may be less than one ten thousandth of the apparent area. The real area of contact is not greatly affected by the size, shape and degree of roughness of the surface: it depends mainly, on the pressure. The general behaviour is consistent with the view that the surfaces are held apart by small irregularities. This means that even with lightly loaded surfaces the local pressure may be sufficiently great to cause the steel to flow plastically. This conclusion is supported by the observed relation between the pressure and the electrical con- ductivity. The slope of such a curve indicates that, at the points of contact, plastic flow of the metal has occurred. Although the stresses may cause elastic deformation in the bulk of the metal, the experiments suggest that the irregularities on which the bodies are supported are crushed down until their cross-section is sufficient to enable them to support the applied load.
Measurements made with moving surfaces show that the area of contact is not constant but is fluctuating rapidly during sliding. A detailed analysis shows a remarkable correlation between these fluctuations and the frictional and temperature
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changes described in an earlier p aper. It is clear that an intermittent clutching and breaking away of the surfaces is taking place and the results support the view that metallic junctions between the metals are being rapidly formed and broken. The nature of these junctions depends on the relative physical properties of the two metals and there is again evidence that three main types may occur.
The conductivity measurements show that even if the metals are lubricated with mineral oils and other lubricants, metallic contact may still occur through the film of lubricant. When the surfaces slide, fluctuations in the area of contact are observed and the behaviour may be essentially the same as for unlubricated surfaces.
Visual pathways concerned in gonadal stimulation in ferrets. By W. E. LE GROS CLARK, F.R.S., T. McKEOWN and S. ZIUCKERMAN. (Received 10 August 1938.)
At the beginning of the non-breeding season lesions were made at various levels in the visual pathways of the brains of female ferrets. The animals were then exposed, at the end of each day, to bright artificial illumination for 6 hr. and 30 min. in order to discover whether or not they would come into heat during the anoestrum. Normal control animals, and ferrets whose optic nerves had been divided were exposed to the same conditions, while normal control animals were also kept under ordinary laboratory conditions.
The ferrets whose optic nerves had been divided either did not come into heat at all, or came into heat much later than the control animals. All the other animals came into oestrus either within or soon after the control period set by the normal animals exposed to additional light. The experiments showed that the normal response to visual stimulation occurs in the absence of the superior colliculi, when all retinal impulses to any part of the mid-brain have been interrupted and when retinal impulses to the dorsal nucleus of the lateral geniculate body and the visual cortex have been completely interrupted. Unless a few isolated normal cells in the dorsal nucleus of the lateral geniculate body provide the basis for adequate cortical stimula- tion, it was also found that a normal response can occur in the combined absence of the visual cortex and the superior colliculi, while another experiment strongly suggested that it can occur even after the interruption of retinal impulses passing to the dorsal nucleus of the lateral geniculate body, visual cortex, superior colliculi and pretectal area. This being so, the conclusion is suggested that the visual response depends on impulses passing either to the ventral nucleus of the lateral geniculate body, or to the subthalamus by way of the accessory optic tracts.
- These results are discussed in relation to views on the exteroceptive stimulation of the pituitary in general and to the question of pituitary innervation in particular.
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