yune 20, 1878] 



NATURE 



215 



give off free chlorine when volatilised at a red-heat, and that the 

 subliaiate contains thallium and chlorine in the atomic ratio of 

 equality. 



In each experiment the total amount of thallium and of 

 chlorine remaining in the globe was determined by analysis, and 

 the specific gravity calculated from their sum. 



Experiment I. ... 



II. ... 



„ III. ... 



„ IV. ... 



V. ... 



„ VI 



„ VII. ... 



The specific gravity of thallium chloride vapour calculated 

 upon the supposition that the molecular weight of the compound 

 is 238'07, and its formula TlCl, is 8"49, 



Four determinations of the specific gravity of mercury vapour 

 made simultaneously with four of the above experiments gave as 

 a mean the number 6'0 instead of 6'728. 



The specific gravity of the vapour of lead chloride was made 

 in a similar way, but the temperature required for complete 

 volatilisation is much higher than that needed in the case of the 

 last compound. The residue left in the globes was completely 

 soluble in hot water, and contained lead and chlorine in the 

 proportion of one atom of the former to 2"o8 of the latter. 



Temperature 



determined 



calorimetrlcally. 



Specific gravity 



of the vapour 



of lead chloride. 



Experiment I. ... 



II. ... 



III. ... 



IV. ... 



... 1046 9*12 



... 1089 972 



••• 1077 9-51 



... 1070 9'64 



The specific gravity calculated from the formula PbCl2=277"i4 

 is 9-62. 



I hope before long to be able to lay before the Society the 

 results of specific gravity determinations of the vapours of other 

 compound and elementary bodies, togettier with the whole of the 

 experimental details. 



Anthropological Institute, May 14. — Mr. John Evans, 

 D.C.L,, F.R.S., president, in the chair. — Capt. Dillon ex- 

 hibited a 'Series of flint implements, collected in the neighbour- 

 hood of Ditchley, Oxfordshire, and a number of others, from the 

 drift gravel of the sea valley near Clapton, were exhibited by 

 Mr. Worthington G. Smith. The following papers were read 

 by the author. Prof. Rolleston, M.P., F.R.S. — Description of a 

 male skeleton found at Cissbury by Mr. J. Park Harrison. The 

 paper was illustrated by a semidiagrammatic of the pit whence 

 the skeleton had come ; the principal parts of the skeleton itself, 

 some bones of ox, goat, pig, and red deer, and finally, a large 

 quantity of worked flints and some lumps of iron pyrites were 

 upon the table. Much help had been received as to the preserva- 

 tion of the skeleton from Dr. Kelly, the Medical Officer of 

 Health for the district. There was no doubt the skeleton had 

 belonged to a man wath a markedly dolichocephalic skull, the 

 length-breadth index being 71, but not tapeinocephalic, the 

 length-height index being 76 ; his stature had been something 

 under 5 feet, either as calculated from the long bones or by 

 .simple measurement of the skeleton as laid out and increased by 

 the addition of one inch for calcaneal and cranial integuments. 

 The age had been something between 25 and 30, the absence of 

 wear on the w-isdom teeth being deceptive owing to the non- 

 development of one of these teeth and the small size of another. 

 The owner of the skeleton had suffered from infantile cerebral 

 hemiplegia, the right humeous being half an inch longer, and the 

 right radms ^" longer than the corresponding bone on the left 

 side, whilst the femur were equal in length, and the right tibia 

 only '^y longer than the left. This pathological condition, how- 

 ever, did not account for some very striking characters of the 

 limb-bone<;, which were equally prominent on both sides of the 

 body : these being the platyenemy of the tibiae, the anterior 

 convexity, and from side to side flattening of the humeri, and 

 the curved upward end of the illux. Altogether the osteologial 

 peculiarities of the skeleton were as distinct evidences for its 

 antiquity as its mode of burial. — On the excavation of three 

 round barrows at Sigwell, near South Cadbury, in the parish 



of Compton, Somerset. These three round barrows belonged 

 to the bronze age, no trace of iron, except such as had been 

 accidently, and demonstrably so, introduced, being found in 

 any of them. The interments in them had been in the way of 

 cremation, and in one case the ashes had been gathered into a 

 bark coffin and a bronze dagger placed with them. In one 

 barrow no interment was found ; in another the ashes occupied 

 an area of only an inch in diameter ; and in both cases the 

 bones had been carefully picked out of the embers of the 

 funeral pile and interred apart, though, in neither case, in an 

 urn. Fragmentary pieces of coarse pottery, however, were 

 found here and there throughout the mass of the barrows, and, 

 though there were no flints to be found in the immediate neigh- 

 bourhood, great abundance of chipped flints and some scrapers 

 were found, and notably one very beautiful one by the Rev. 

 J. A. Bennett, to whose association very much of the success of 

 the exploration was due. 



Physical Society, May 11. — Prof. W.G.Adams, president, 

 in the chair. — The following candidate was elected a Member of 

 the Society : Rev. P. Magnus, B.A., B.Sc — Mr. J. Norman 

 Lockyer, F.R.S., read a paper on some recent researches in solar 

 chemistry, a report of which is deferred for the present. — Sir 

 William Thomson, LL.D., F.R.S. , described and exhibited 

 the apparatus he has employed in recent researches on the in- 

 fluence of stress on magnetisation, a detailed account of which 

 he has submitted to the Royal Society ; he also, in part, 

 described them at the Royal Institution on May 10, but at- 

 tention was not then directed to the experimental details now 

 brought before the Society. The rod or wire under examination 

 was surrounded by two co-axial wire helices, the outer of which 

 was connected with the battery, and the inner with a ballistic 

 galvanometer, that is, one that acts with regard to electric 

 impulses just as Robins' ballistic pendulum. It was some years 

 ago discovered by Villari that a longitudinal pull augments the 

 temporarj- induced magnetism of soft iron bars or wires when 

 the magnetising force is less than a certain critical value, and 

 diminishes it when the magnetising force exceeds that value ; in 

 either case the residual magnetism is augmented when the force 

 is applied and diminished when it is removed. Sir W. Thomson 

 has found the critical value for soft iron to be about twenty-four 

 times the vertical component of the earth's magnetic force. It 

 is therefore approximately 10 C.G.S. units. In the case of some 

 bars of nickel and cobalt specially prepared for him by Mr. 

 Wharton, of Philadelphia, he finds opposite effects. With the 

 amounts of magnetising force used the effect of pull was to 

 diminish magnetisation, but the amount of this effect \vas less 

 ^^■ith the highest magnetising forces than with a certain degree of 

 magnetising force which was found to make it a maximum with 

 probably or possibly a critical value. But this value had not 

 been reached by the magnetising force hitherto applied. The 

 next branch of the inquiry had reference to the transverse 

 stress obtained by water pressure within a gun-barrel, and it 

 was ascertained to have opposite effects to those found by 

 Villari in the case of longitudinal pull. The critical point 

 in soft iron for transverse pull is at about 25 C.G.S. units. 

 Sir W. Thomson has been examining the effect of torsion on 

 a wire that is at the same time exposed to longitudinal pull, 

 confining himself in his first set of experiments to magnetisation 

 under the sole influence of the vertical component of terrestrial 

 magnetism. His results showed, with every amount of longitu- 

 dinal pull, a diminution of magnetisation produced by torsion in 

 either direction, thus extending a conclusion arrived at by Mat- 

 teucci, Wertheim, and Wiedemann, regarding the effect of torsion 

 unaccompanied by longitudinal stress. But it now appears that 

 this effect of torsion is very remarkably diminished by a large 

 pulling force nearly reaching the limits of elasticity. In con- 

 clusion. Sir W. Thomson called attention to a very different and 

 extremely interesting effect of torsion discovered by Wiedemann 

 — the development of longitudinal magnetisation in an iron wire 

 by twisting it while a current of electricity is flowing along it. 

 This effect, he pointed out, is just what would result from the 

 seolotropic susceptibility for magnetisation due to the oeolotropic 

 stress produced in the outer portion of the wire by the torsion, 

 supposing the tangential magnetising force to be less than a 

 certain critical value intermediate between the Villari critical 

 value and the more than twofold greater critical value which Sir 

 W. Thomson has found for transverse magnetising force.. But 

 he pointed out that another cause was also positively or. nega- 

 tively efficient in contributing to Wiedemann's result. This cause 

 is the difference of electric conductivity in different directions 



