Abstracts of Papers Communicated to the Royal Society of London

Abstracts of Papers Communicated to the Royal Society of LondonSource: Proceedings of the Royal Society of London. Series A, Mathematical and PhysicalSciences, Vol. 165, No. 923 (Apr. 27, 1938), pp. S45-S56Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/97042 .

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ABSTRACTS

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 publication 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-".

27 APRIL 1938

The structure and relations of the human premaxilla. By E. H. JOHNSON. (Communicated by F. Wood Jones, F.R.S.-Received 10 March 1938.)

The structure and relations of the human premaxilla have been described. It has been shown to be vestigial in character compared with the homologous bones in lower animals.

The premaxillae are completely covered on the facial aspect by the incisor processes of the maxillae. "Suture lines" on the facial surface have been shown to be due to superficial fissures between the ridges of developing bone on the frontal process of the maxilla. From the conditions observed in the region of the floor of the nasal cavity, it seems that the double narial margins which occur in prognathous races are attributable to an incomplete passage of the incisor processes of the maxillae towards the anterior nasal spine.

The anterior alveolar walls of the incisor teeth are maxillary. The ascending process of the premaxilla becomes entirely restricted to the internal

nasal surface of the maxilla, because of relative differences in the rate of bone growth in this region. In cleft palate, the variation in position of the cleft is not due to a division through the premaxilla, but to the lateral incisor and its alveolus becoming displaced to the lateral side of the cleft. Pathological " exfoliation of the premaxilla" is not indicative of its structural form.

The premaxilla in man has been compared with that in other Primates and has been shown to differ in form, relations, and the time of closure of the sutures. The peculiar shutting off of the premaxilla on the face by the incisor processes of the maxillae is to be regarded as a specific character of man.

Abstracts [S 45] 7



S 46 Abstracts of Papers

The distribution of carbon dioxide in the hen's egg. By J. BRoOKS and J. PACE. (Communicated by Sir Joseph Barcroft, F.R.S.-1Received 14 March 1938.)

The combined CO2 of egg-white in equilibrium with different partial pressures of C02 was measured over the range p = 005-1P0 atm. CO2 at 250 C. An increase in CO2 pressure increased the concentration of combined CO2. It was assumed that the combined CO2 was present in the form of bicarbonate. On this basis the buffer value per g. protein was 4-8 x 10-5 for thepH range 6 6-7 8. The reasonable values calculated for the pH of the white and the buffer value of the proteins supports the assumption that the amount of carbamino-CO2 present is small.

The value of the Bunsen solubility coefficient for CO2 and white at 250 C. was 0-71. This value is about 8 % greater than the value calculated from the salt and water content of the white. It is suggested that, as in blood serum, the excess solubility is caused by the presence of traces of lipoids.

The uptake of CO2 by shell and yolk was measured. The retention of C02 and buffer values of egg-white and the relation between the salts of shell and white have been discussed.

Radioactive nodules from Devonshire. By M. PERUTZ. (CoMmunicated by J. D. Bernca, F.R.S.-Received 15 March 1938.)

Globular concretions surrounded by bleached haloes are found in Permian Beds west of Budleigh Salterton, Devonshire. Sections show that their internal structure is complex, a sandy matrix being impregnated by a black hard material in radial and concentric sheets. Contact photographs of a plane section show a distribution of radioactive material closely connected with the structure of the black impregnation. From measurements of the intensity of the radioactivity on an ionization counter a content of 0 4 % uranium was calculated and later confirmed by chemical analysis.

The physical properties of the black part are caused by an apparently amorphous impregnation of vanadium oxides, various other ores also being present in smaller concentrations. Three classes of nodules are described and the possibilities of their origin are discussed.

The last part contains a chemical and geometrical description of the bleached haloes, and after discussion of explanations of their formation suggested by earlier authors the ionizing effect of radon is proposed as an agent which might be partly responsible for the bleaching.

Application of reciprocity to nuclei. By M. BORN. (Communicated by E. T. Whittaker, F.R.S.-Received 15 March 1938.)

The formula for the distribution of quantum states, which follows from the principle of reciprocity and the assumption of a closed p-space, is applied to some properties of nuclei. The results can be considered as confirmations of the hypothesis. The mass of a particle moving with velocity of light and maximum momentum is of the same order as that of the particles which Yukawa has introduced.



Abstract& of Papers S 47

Classical theory of radiating electrons. By P. A. M. DIRAO, F.R.S. (Received 15 March 1938.)

The object of the paper is to set up in the classical theory a self-consistent scheme of equations which can be used to calculate all the results that can be obtained from experiment about the interaction of electrons and radiation. The electron is treated as a point charge and the difficulties of the infinite Coulomb energy are avoided by a procedure of direct omission or subtraction of unwanted terms, somewhat similar to what has been used in the theory of the positron. The equations obtained are of the the same form as those already in current use, but in their physical interpretation the finite size of the electron reappears in a new sense, the interior of the electron being a region of space through which signals can be transmitted faster than light.

Self-consistent field with exchange for calcium and argon. By D. R. HARTREE, F.R.S. and W. HARTREE. (Received 16 March 1938.)

The differences between the atomic wave functions calculated by the method of the self-consistent field with and without exchange can in certain cases be plotted in such a way that the results for different atoms fall on approximately the same curve, which then can be used for interpolating between different atoms.

Wave functions so estimated using the results already calculated for Cl- and Ca++ have been used as the basis of calculations of the self-consistent field for K+ and Ar. For K? all the (nl) wave functions have been calculated; the results showed that for Ar all but the outer [(3s) and (3p)] wave functions could be interpolated to adequate accuracy by the method mentioned.

Results are given, and values of the diamagnetic susceptibilities calculated and compared with observed values.

Studies of the post-glacial history of British vegetation. By H. GODWIN and M. H. CLIFFORD. (Communincated by Sir Albert Seward, For.Sec.R.S.- Received 16 March 1938.)

The plant remains of the fen deposits have been analysed, and stratigraphy has been determined from profiles and from extensive borings: the methods of pollen analysis have been employed to indicate the drift of local vegetation phases on the fens themselves.

Part I deals with the Woodwalton Fen area, a part of the fenland margin south of Peterborough, where the fen peats have been little damaged by drainage and peat cutting. It is shown that on the landward side there is a single peat bed, which is separated into two not far from the fen margin, by the tapering edge of a bed of fen clay shown by foraminiferal and diatom analysis to have been laid down in brackish water. This clay, which must have represented a marine transgression, interrutpted a phase of extensive development of fen woods, at first mainly alder-oak, and later pine-birch. Tree remains are very abmndant. The peat above the fen clay showed clear




evidence of the development of acidic sphagnum peat of the kind found only in raised bogs ("i Hochmoore "). This type of peat was previously unrecognized in the fens, and it reflects conditions of freedom from flooding by alkaline water. It is probable that this phase corresponds with the Bronze Age, and that in the succeeding Tron Age conditions changed sharply. The acid sphagnum peat is overlaid by the calcareous lake marl of Ugg Mere and Trundle Mere, lakes which were only recently drained. They are thus shown to have had a very recent origin.

Part II of the paper extends the observations in the Woodwalton area towards the sea and towards the southern half of the fens. A series of long sections has been constructed which converge towards Wisbech (upon the main estuary of the last phase of fen history). These sections show that the upper and lower peats, separated by the fen clay, occur regularly and continuously over the entire area. On the seaward side they are overlaid by an upper layer of semi-marine silt deposited in the Romano- British period. By a long series of shallow bores the above series of sections was tied to the known profiles at Wood Fen, Ely. Thence it was clear that the phases of lower peat, fen clay, upper peat and upper silt could be accepted as broad major divisions across the whole of the- southern part of the Fenland.

Peat formation in the Boreal period was restricted to places of local wetness, such as deep river valleys. A dry phase at the Boreal-Atlantic transition corresponded with a late Tardenoisian culture horizon. Peat formation became general in the fens in the Atlantic period, and the fens became wooded in the Neolithic period, during the end of which time, or just after which, there was an extensive but shallow marine transgression which caused the fen clay to be formed. The succeeding period in the fens began with "A" Beaker culture and during the Bronze Age they were dry: the fens were either wooded or formed raised-bogs, and were fairly habitable. The ensuing Iron Age must have been wet. The Roman period was marked by the deposition of considerable thicknesses of semi-marine silt in a wide belt on the seaward side of the fens, and in tongues along the courses of the estuaries. There were human settlements upon the silt whilst it was forming, and its present surface shows the remains of dense occupation. The great meres of the, Fenland probably formed either in the Iron Age or the Romano-British period.

On the theory of scattering of light. By HANS MUELLER. (0ommUnicated by R. H. Fowler, F.R.S.-Received 16 March 1938.)

The Krishnan effect can be explained if the fluctuations of the optical anisotropy in the medium are not independent in neighbouring volume elements. By applying Brillouin's method to longitudinal and transversal waves the Krishnan effect is calculated for arbitrary directions of observation. It is found that the reciprocity relation is always valid. Every substance which has a Krishnan effect should show a Mie effect. Both effects are related to the photoelastic properties in the case of solids, and to the constants of streaming birefringence in the case of liquids.

The Krishnan and Mie effects must occur for temperature scattering in solids. In isotropic solids the scattered light must consist of two pairs of Doppler components, for crystals three different Doppler shifts can be expected. The Kris an effect can



Abstracts of Papers S 49

occur in ordinary liquids if Lucas' transversal waves give a noticeable contribution to the scattering. For temperature scattering the depolarization ph = V/Hh is always larger than 1.

A new theory of the scattering of light in glasses is proposed. It is based on the assumption that glasses contain a random distribution of " frozen in " strains. Slightly below the solidification temperature these strains are normal ones, but at lower temperatures shearing strains are created due to temperature contraction. Ph is smaller than 1 because the shearing strains are always smaller than the normal strains. It is found that Krishnan's data are in excellent agreement with those calculated for glasses for which the photoelastic constants are known.

Liquids with molecular clusters can be treated as if they were uniform liquids with a distribution of internal strains. They show ph, < 1 because the strains are pre- dominantly normal ones. A relation between the Mie effect for critical opalescence and the deviation from the -4 law is found to agree with Rousset's observation.

It is pointed out that scattering data furnish a Fourier analysis of the optical variations within the medium and can be used to determine the size of molecular clusters and of colloidal particles.

Gans' theory of scattering by molecular clusters is discussed and it is shown that it agrees with Krishnan's reciprocity relation.

The two-stage auto-ignition by hydrocarbons. By G. P. KANE. (Com- municated by A. C. G. Egerton, F.R.S.-Received 17 March 1938.)

Previous investigations into the spontaneous ignition under pressure of the higher paraffins and olefins containing more than three carbon atoms have shown that in the temperature range between ca. 270-400? C., ignition occurs by a two-stage process preceded by an induction lag t_ before the formation of a cool flame and a second lag t2 before the subsequent ignition of the cool flame products; increasing pressure shortens both these lags, and although kinetic relationships have been developed it has not been possible adequately to test them owing to the extreme violence of the ignitions at pressures much above the minimum ignition pressure.

An optical recording manometer is described whereby it has been possible to measure tl and t2 at pressures up to 15 atm. with an accuracy of 1/100th of a second.

With propane, t2 decreases more rapidly than t1 with increasing initial pressure and at a critical pressure (about 8 atm.) the two-stage is replaced by a single-stage process; the induction lag then decreases very rapidly with pressure with propylene, where the induction lags are much greater, no such transition had occurred at pressures up to 12 atm.

The bearing of these results both on the nature of the kinetic processes operative and on the problem of "knock", is briefly discussed.



S 50 Abstracts of ;Papers

The morphology of the brachial plexus, with a note on the pectoral muscle, and the twist of its tendon. By W. HARRIS. (CoMmunicated by W. Trotter, F.R.S.-Received 17 March 1938.)

The primary or ventral divisions of the spinal nerves subdivide again into dorsal and ventral nerves to supply the dorsal and ventral muscles and skin of the limb, dorsal joining dorsal and ventral joining ventral divisions.

The simplest type of plexus consists of two cords, dorsal and ventral, formed by the union of the dorsal and ventral subdivisions of all the primary nerves entering the plexus, as in frogs and toads, and in birds. In mammals the original ventral cord, and to a less extent the dorsal cord becomes split up into different nerve trunks, though dorsl and ventral nerves remain apparently strictly apart.

Examination of the reptilian type of plexus in salamanders, turtles, lizards, crocodiles and the Monotremata demonstrates the passage of dorsal fibres into the median and ulnar branches of the ventral cord, probably for convenience of carriage, facts which suggest that essentially dorsal fibres in Man must enter the ventral trunks early, and thus explain the dorsal cutaneous and muscular supply in the hand by the median and ulnar nerves in Man.

The marsupial plexus is a primitive mammalian type, and varies little with the structure of the animal.

Short-necked mammals like the manatee and the Cetacea have five to seven nerves in the plexus, and long-necked forms like the llama and horse have a compressed plexus.

The Carnivora and quadrupedal Ungulata have lost the fifth cervical nerve from the plexus.

The second dorsal nerve may be considered to be a disappearing feature in the mammalian plexus.

In the Primates with arboreal life and increasing use of the deltoid, the fifth cervical nerve reappears and the plexus becomes increasingly prefixed up to the anthropoids, and the pectoral muscle develops a twist of 1800 in the tendon of its lower half, aiding the power of climbing.

The nuclear magnetic moment of copper. By S. TOLANSKY and G. 0. FORESTER. (Communicated by P. M. S. Blackett, F.R.S.-Received 18 March 1938.)

The doublet hyperfine structures of the resonance lines of the copper spectrum, A 3247 and A 3274, have been measured with a quartz Lummer plate. The lines are produced free from reversal effects, the doublet separations being respectively 379 and 405 x 10-3 cm.-'. The following hyperfine structure interval factors are calculated. 3d'0 4s 1 2S -197-5, 3d'0 4p 22p* = 14 and 3d'0 4p2 =2p 4 8 (all in cm.-' x 10-3). The mean nuclear magnetic moment for the two copper isotopes, 63 and 65, is derived from the ground state, 3d10 4s 1 2S1. The value found is 2 _ 247 nuclear magnetons, this being probably a better estimate than that given by other terms, since the ground state is spherically symmetrical and thus not affected by quadrupole moment of the nucleus. By adopting Schiller and Schmidt's value for the ratio of the magnetic moments of the two isotopes, it is found that #ct Cu63 = 243 and It Cu65 = 2-54 nuclear magnetons.




The disintegration of boron by slow neutrons. By C. O'CEALLAIGH and W. T. DAviES. (Communicated by E. V. Appleton, F.K.S.-Received 18 March 1938.)

The disintegration of boron by slow neutrons-rBI+ nI= Li7 +B2H+e4 + Q1-has been studied in an expansion chamber. Evidence has been found for the emission of three groups of heavy particles of ranges 4-25 + 0-2 mm., 7-15 ? 0-25 mm. and 8-9 + 0-4 mm. in air at 15? C. and 760 mm. The 4-25 mm. group is clearly due to the lithium nucleus. On the basis of the recent range-energy determinations of Blewett and Blewett, the 7-15 and 8-9 mm. groups, which must consist of oa-particles, would lead respectively to energy releases of 2-45 and about 3 x 106 e-volts. Substitution in the equation of reaction of the masses at present accepted leads to a value for Q, of 2-99 x 106 e-volts. The 8-9 mm. cx-particles would correspond, therefore, to the production of the Li7 nucleus in the ground state, and the 7-15 mm. particles to an excited nucleus having an energy of 0-55 ? 0-15 x 106 e-volts above the ground state.

Evidence based on the emission of two groups of protons in the reaction

3Li6 +D2 = 3Li7+1Hl

leads to the prediction of one low-lying excitation level of Li of 0-44 x 106 e-volts. This is confirmed by absorption measurements on the y-radiation accompanying this disintegration. Our value 0-55 + 0-15 x 106 e-volts is in satisfactory agreement with the above figure. A study of the y-radiation arising from the non-capture excitation of Li7 by a-particles would seem to indicate the presence of two low-lying excitation levels of 0-6 and 0-4 x 106 e-volts, but itispossiblethat transitionsto the 0-6 x 106 e-volts state are not allowed in the above reactions.

The heteropycnosis of sex-chromosomes and its interpretation in terms of spiral structure. By M. J. D. WXITE. (Communicated by J. B. S. Haldane, F.R.S.-Received 22 March 1938.)

There appear to be two kinds of heteropycnosis met with in the chromosomes of the Orthoptera saltatoria, which may be called the reversible and non-reversible types. In the reversible type the same chromosome may show both positive and negative heteropyonosis at different stages. In the non-reversible type only positive heteropycnosis is seen. During negative heteropycnosis the chromosome does not undergo as much thickening as in the "control" autosome. In positive heteropycnosis the chromosome undergoes more thickening.

Both positively and negatively heteropycnotic chromosomes have a spiral structure at metaphase. The number of gyres in the spiral per unit length is believed to be inversely proportional to the diameter of the chromosome, so that it will be greater in negatively heteropycnotic chromosomes than in positively heteropycnotic ones. The direction of coiling of the spiral is not constant in the X-chromosomes of the Tettigonidae, i.e. the same chromosome may show either right-handed or left-handed coiling. In the spermatogonial divisions the direction of coiling may be reversed at the spindle attachment of the chromosome or elsewhere.




A new and anomalous type of meiosis in a mantid. By M. J. D. WIwPE. (Communicated by J. B. S. Haldane, F.R.S.-Received 22 March 1938.)

The meiosis of Callimantis takes place in a manner which is entirely unique. No chiasmata are formed and the first meiotic division is consequently reductional for all parts of the chromosomes. The usual diplotene and diakinesis stages are completely absent. Unlike other mantids hitherto studied this species (C. antillarum SauSs.) is XO in the male.

The problem of n bodies in general relativity theory. By Sir ARTHUR

EDDnIGTON, F.R.S. and G. L. CLARK. (Received 22 March 1938.) The motion of a system of two bodies (e.g. a double star) is investigated s far as

terms of the second order in the potentials. Contrary to a result obtained by Levi- Civita in 1936, we find no -secular acceleration of the centre of mass of the system.

The work revealed an error in the standard formulae for the line-element of a system ofn bodies, given by de Sitter in 1936. As a result of correcting the error, the equivalent mass M of the system is found to be

M = E + 4d2C/dt2,

where E is the energy (including potential energy) and C the moment of Inertia about the centre of mass.

The secretion of crystalloids and protein materlal by the pancreas. By S. A. KUMAROV, G. O. LANGSTROTH and D. R. MCRAE. (Communicated by J. S. Foster, F.R.S.-Received 25 March 1938.)

The concentrations of Na, K, Ca, Cl, HCO1, and protein and non-protein nitrogen, were determined in series of samples of pancreatic juice secreted by dogs in, response to (a) constant rate of administration of secretin, (b) varied rate of administration of secretin, and (c) interrupted administration of secretin (rest period, 2 hr.). The use of quantitative spectroscopic methods of analysis in the determination of the metals, and of absorption spectrum methods in, the study of the protein composition of the secetion, were important features of the technique.

The fact that the observed concentrations of metals in the secretion are independent of the degree of activity of the gland, is considered to indicate that the glandular membranes offer little resistance to the passage of simple inorganic ions. The apparent marked differences in permeability to different ions, s indicated by Ball's (1930) injection experiments, are probably due to a transformation of part of the injected substances to " non-diffusible" forms in the blood stream.

The observed increase in the bicarbonate concentration with inereasing rate of secretin administration, and the compensatory relation with the chloride oncentra- tion, is interpreted on the bsis of (a) the formation of at least a part of the bicarbonate as a product of metabolism within the glandular cells, and (b) the action of membrane forces, probably of an electrical nature.



Abstracts of ers S 53

A correlation of absorption spectrum measurements with protein nitrogen data admits of two alternative interpretations; (a) only one type of absorbing protein is present in the secretion, and a part of all of this serves as a carrier for enzymatically active groups, or (b) several types of absorbing protein are present, and these, whether enzymatically active or not, are always secreted in constant proportions.

The interpretation of protein nitrogen and certain other data is given in the accompanying paper.

The processes of synthesis and secretion of protein material in the pancreas. By S. A. KUMAROV, G. 0. LANGSTROTH and D. R. MCRAE. (Gommunicated by J. S. Foster, F.R.S.-Received 25 March 1938.)

A theory of the process of synthesis of protein material by the pancreas, and its secretion in response to secretin administration, is developed. The theory leads to expressions which describe quantitatively the behaviour of the protein output in samples of secretion obtained under widely varied experimental conditions. It permits some insight into the fundamental nature of certain of the glandular processes, as well as the calculation of various factors not directly observable in critical experi-- ments. It is rich in suggestions for new problems in connexion with the secretory processes.

The applicability of the Gibbs' adsorption theorem to solutions whose surface tension curves exhibit minima or horizontal portions. By J. W. McBAIN, F.R.S. and G. F. MIILs. (Received 25 March 1938.)

The classical Gibbs' adsorption theorem appears to be a limiting law applying to cases where mutual repulsion or oriented dipoles upon the surface and the effects of submerged double layer and of electrification do not also condition the surface tension.

All aqueous and ionizing systems involve the important factor of a submerged double layer of greater or lesser development, powerfully affecting the surface tension, appreciable even for insoluble oil films on water or for pure water itself.

Abundant examples of "Type 3" surface tension curves have been obtained by many authors by every experimental method. In these, the static or true equilibrium surface tension is very greatly lowered in extreme dilution, thereafter remaining constant or passing through one or more maxima or minima, although the dynamic or immediate surface tension is several times greater, nearly that of water. Application of the classical Gibbs' theorem in its exact form to these cases yields a series of. obviously impossible results, no matter in what form they are calculated. The different reasons adduced by many authors for avoiding such applications are seen to be gravely at varinnce with the foundations of chemical thermodynamics.

The factors of orientation and submerged double layer omitted in the Gibbs' formulation are indicated.

It follows from the Gibbs' equation that the surface of solutions of soluble suLbstances is very deep as compared with molecular dimensions, in contrast to the familiar conception of insoluble films on water.



S 54 Abstrats of Papers

The first spark spectrum of platinum. By A. G. SHENSTONE. (CoMMUni- cated by R. H. Fowler, F.R.S.-Received 25 March 1938.)

The paper reports observations on the Spectrum Pt II and classifies a large number of levels. A list of lines is also given including (i) all identified lines between A976 and A 1242, (ii) all certain low transition lines and all identified high transition lines between A 1242 and A4514.

The adsorption of vapours at plane surfaces of mica. Part II. Heats of adsorption and the structure of multimolecular films. By D. H. BANGIJAM

and S. MOSALLAM. (Communicated by D. L. Chapman, F.R.S.-Received 25 March 1938.)

The results are given of measurements of the quantities of benzene, methyl alcohol, and carbon tetrachloride adsorbed at a known surface area of mica at pressures approaching saturation. The adsorption energy is constant whilst the first molecular layer is being formed, but its completion is marked by an abrupt decrease to a value near the normal heat of liquefaction. The graphs of apparent film thickness against relative pressure for the three substances are not widely divergent over much of the range investigated, but the isotherms show discontinuities or sharp changes of curvature at adsorption values which are thought to be related to molecular spacings in the bulk condensed phases. Approximate values are given for the surface tension lowering of the mica, caused by the saturated vapours.

The swelling of charcoal. Part V. The saturation and immersion expansions and the heat of wetting. By D. H. BANGHAM and R. I. RAZOUK. (Com- municated by D. L. Chapman, R.B.S.-Received 25 March 1938.)

The percentage linear expansion x, of a rod of inactive wood charcoal when exposed to the exactly saturated vapour of methyl alcohol is found to be less than the expansion xL produced by immersion in the liquid. The expansion is proportional to the surface energy lowering of the charcoal, and this relation is confirmed by comparing

(xL -T dx) with the measured heat of wetting. On immersion of the air-free

charcoal the liquid wets all, or nearly all, of the adsorbing surface. From well- supported estimates, previously given, of the specific surface of the charcoal, it becomes possible to assign values to the free and total energy changes per cm.2 which accompany saturation and immersion.




The crystal structure of certain bridged palladium compounds. By A. F. WELLS. (Communicated by J. D. Bernal, F.R.S.-Received 26 March 1938.)

The crystal structures of the bridged compounds [(CH3)3As]2Pd2Cl4 and its bromine analogue have been determined. The crystals of the tetrachloride from alcohol and from dioxane and those of the tetrabromide from dioxane are all isomorphous. A probable structure deduced from the optical properties, cell dimensions and symmetry was confirmed by Fourier projections using visually estimated intensities. The structure of the tetrabromide was investigated in detail, the configuration of the molecule being finally obtained from a section of the three-dimensional electron density distribution. The bridged molecule is found to be planar with the configuration

(CH3)3 As Br Br Pd 860 Pd 860

Br BrZ NAs(CH3)3

The interatomic distances are: Pd-Br 2-45 and Pd-As 2 50 + 0 05A. The molecules are stacked in columns along 42 axes in the space group I 4/rn, and the columns of molecules are held together by very weak van der Waals forces. The packing of the molecules in this way leaves tunnels through the structure. These remain empty in certain circumstances, as, for example, when the tetrachloride crystallizes from alcohol. On crystallizing from dioxane, however, this compound takes up dioxane of crystallization presumably owing to the fact that the diameter of the dioxane molecules is approximately the same as that of the holes in the structure. The introduction of the solvent is accompanied by a small increase in the cell size and a slight reorientation of the molecules of the palladium compound.

The paramagnetic magneton numbers of the ferromagnetic elements. By W. SUCKSMITH and R. R,. PEARCE. (CoMmunicated by A. M. Tyndall, F.R.S. -Received 28 March 1938.)

A method is described for measuring magnetic susceptibilities in a controlled atmosphere or in vacuo at temperatures up to 1500? C. The special precautions required to prevent solid diffusion and minimize evaporation in measurements on metals are discussed. Accurate measurements on the susceptibilities of the ferromagnetic elements, hitherto confined to nickel, are extended to cobalt and iron. The magnetonrnumbers for both these elements are deduced to an estimated accuracy of 1-2 % from the experimental data. It is shown that the existing theory is inadequate to explain the new results obtained.

Electromagnetic induction in non-uniform conductors, and the determination of the electrical conductivity of the earth from terrestrial magnetic variations. By A. T. PRICE and B. N. LAHIRI. (Communicated by S. Chapmnn, F.R.S.-Received 28 March 1938.).

The results of previous investigations by Chapman and Price of the induced fields and current distributions, associated with the magnetic daily and storm-time variations, suggest that more precise information as to the distribution of electrical




conductivity (K) Within the earth, might be obtained by considering electromagnetic induction in a non-uniform sphere. The general theory for any non-uniform conductor is here considered, and the formal solution for any conductor with spherical symmetry is obtained. Detailed formulae for the induced field and current distribution, in the special case when K =kp-m, where k and m are constants, are obtained and applied to the terrestrial magnetic variations. The results obtained support the view, expressed by Chapman and Price, that there is a considerable increase of K with increasing depth, beyond 150 km. It seems, however, that the really important increase in K takes place at about 700 km. depth, beyond which K is at least as great as 10-"1 e.m.u., while above this depth the mean conductivity may be of the same order as for rocks on the earth's surface (10-16 or 10-15 e.m.u.). This suggests that there is some change in the composition of the earth (e.g. to a more metallic content) at a depth of about 700 km.; seismological evidence appears to indicate that such a transition occurs at a somewhat greater depth. The results also show that there is an effective distribution of K at or near the surface of the earth, and it seems most probable that this represents the influence of the relatively highly conducting oceans. The induced currents do not penetrate appreciably beyond a depth of about one-fifth of the earth's radius, so that the knowledge of K afforded by the daily variations and the storm-time variations will be restricted to an outer shell of this thickness.

The photochemical polymerization of methyl acrylate vapour. By HI. W. MELVILLE. (Communicated by E. K. Rideal, P.B.S.-Received 28 March 1938.)

The photopolymerization of methyl acrylate vapour has been studied at pressures up to 60 mm. and at temperatures between 20 and 150? C. Polymerization occurs almost quantitatively, giving a dense cloud of polymer in tthe gas- phase when about 10 quanta are absorbed/c.c./sec. at 2537 A, the quantum yield ranging from unity to 5000 depending on the temperature and intensity. At shorter wave-lengths the molecule is dissociated to hydrogen and propiolic ester. Growth of the polymer ceases when two growing polymers interact with each other. The. temperature of this latter process is so large that the polymerizatidn has a negative temperature coefficient.

The reaction is very sensitive to inhibitors especially to oxygen and to a lesser extent butadiene. By controlled use of inhibitors, a direct measure of the energy of activation of the propagation reaction has been made: it amounts to 4 k.cal. At high oxygen pressures, oxygen exerts a positive catalytic effect believed to be due to the mercury sensitized production of 0 atoms.

The molecular weight of the polymer has been estimated by measuring the ratio of acrylate to butadiene molecules used up in the inhibited reaction under a given intensity of illumination. Hence by calculation the molecular weight of the product in the normal reaction is easily found.

This behaviour of acrylate is in marked contrast with that exhibited by methyl methacrylate, the long life-time of the latter polymer being absent in the acrylate. Like the methacrylate the acrylate grows by the double bond mechanism and the differences in behaviour of these two molecules is accounted for by the theories advanced in this and previous papers.



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Abstracts of Papers Communicated to the Royal Society of London

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