April I, 1875] 



NATURE 



439 



flaming of the oi), and may at any rate lead to accident as already 

 described, by the alarm which it occasions to nervous or ignorant 

 persons. 



{To be continued^ 



SOCIETIES AND ACADEMIES 



London 



Royal Society, March 18 — "On the Behaviour of the 

 Hearts of Molluscs under the influence of Electric Currents." 

 By Michael Foster, M.D., F.R.S., and A. G. Dew-Smith, B.A. 

 The observations were made chiefly on the heart of the com- 

 mon snail. 



An interrupted current, applied directly to the ventricle (or 

 auricle), and of such a strerglh as not to cause tetanic contrac- 

 tions, produces, as has already been pointed cut, distinct inhi- 

 bition, altogether similar to that brouybt about in the vertebrate 

 heart by stimulation of the pneumogastric nerve. • 



Single induction-shocks, of a strength insufficient to cause a 

 contraction, produce no appreciable effect, in -fthatever phas-eof 

 the cardiac cycle they are thrown in ; but two or more such 

 shocks, the one following the other at a sufiSciently short inter- 

 val, produce a slight inhibition ; that is, the succeeding diastole is 

 prolonged. 



When a constant current of sufficient intensity is thrown into 

 the ventricle at rest, a contraction or "beat" is observed at 

 both the making and the breaking of the circuit. But the 

 initial, making, beat starts frono, and is confined to the region 

 of, the kathode, while the final, breaking, beat starts from and 

 is confined to the region of the r node. This is the case what- 

 ever be the position of the electrodes. 



A constant current of sufficient intensity to bring about a 

 making and a breaking beat when applied for, say five seconds, 

 may be applied momentarily without producing any beat at all. 

 The constant current, therefore, requires some considerable 

 time to develop its maximum effect. 



When a constant current is applied to a spontaneously beating 

 ventricle, a polarisation of the ventricle results of such a kind 

 that the region of the kathode is thrown into a condition which 

 the authors would wish at present not to define more strictly 

 than by saying that it is "favourable to the production of a 

 rhythmic beat," while the region of the anode is thrown into 

 an opposite condition, unlavourable to the production of a rh)th- 

 mic beat. 



On the withdrawal of the current a rebound takes place at either 

 electrode, the kathode region becoming for a time unfavourable 

 to the production of beats, the anode favourable. 



Of these two conditions, the one unfavourable to the pro- 

 ('uction of beats, whether it be in the anodic region during the 

 pass.ige of the current, or in the kathodic region during the 

 rebound, is more easily produced by slight currents than its 

 opposite. Hence the total effect of a slight current, the balance 

 of the opposing agencies, is unfavourable to the production of 

 the rhythmic beat. 



Consequently, when a current, as in a single induction-shock, 

 is applied for so short a time that its maximum effect is not 

 reached and no direct kathodic contraction or beat is called 

 forth, the net result is a hindrance te the rhythmic beat, or, in 

 other words, an inhibition, which may be too slight to be recog- 

 nised with a single «hock, but becomes evident when the shock 

 is repeated after a not too long interval, and is very marked 

 when several shocks rapidly follow each other as in the ordinary 

 interrupted current. 



The main results obtained with the snail's heart were corro- 

 borated by observations on the hearts of Sepia and Aplysia. 



In conclusion, the authors regarding the rhythmic beat of the 

 snail's heart (which they believe contains no differential nervous 

 structures) as a purely protoplasmic movement, call attention to 

 what may be called the principle of physiological continuity, 

 and offer suggestions towards defining the exact function of the 

 intrinsic ganglia of the vertebrate heart, and of other spon- 

 taneously beating organs. 



"On the Liquation, Fusibility, and Density of certain Alloys 

 of Silver and Copper." By W. Chandler Roberts, Chemist of 

 lire Mint. Communicated by Dr. Percy, F.R.S. 



The author states that the most remaikable physical properly 

 of silver-copper alloys is a molecular mobility, in virtue of which 

 certain combinations of the constituents of a molten alloy become 

 segregated from the mass, the homogeneous character. of which is 

 thereby dtslroyed. These inegularities of composition have long 



been known, and reference is made to them in the works of 

 Lazarus Erckern (1650), and of Jars (1774). A very complete 

 memoir was published in 1852 by Levol, who did much towards 

 ascertaining the nature and defining the limits of this molecular 

 mobility. He discovered the important fact that an alloy con- 

 taining 71-89 per cent, of silver is uniform in composition. Its 

 chemical formula (AgjCu^) and peculiar structure led him to 

 conclude that all other alloys are mixtures of this, with excess of 

 either metal. 



The electric conductivity of these alloys was studied in i86o 

 by Matthiessen, who doubted the accuracy of Levol's theory, 

 and viewed them as "mechanical mixtures of allotropic modifi- 

 cations of the two metals in each other." 



The author then describes the experiments he made vifith a 

 view to deteririne the melting points of a series of these alloys. 

 He adopted Deville's determination of the boiling point of zinc 

 (1040° C.) as the basis of the inquiry, and ascertained by the 

 method of mixtures, the mean specific heat of a mass of wrought 

 iron between 0° C. and the melting point of silver, which, as 

 Becquerel showed, is the same as the boiling point of zinc. 



The mean of three experiments, which were closely in accord- 

 ance, gave 0-I5693 as the specific heat of the iron ; and it should 

 be pointed out that this number includes and neutralises several 

 errors which would affect the accuracy of the subsequent deter- 

 minations. 



Melting points of several alloys were then determined by 

 plunging an iron cylinder into them and transferring the iron to 

 a calorimeter. These melting points varied from 840° C. to 

 '^i^P'' C., or through a range of 490° C. The alloys which 

 occupy the lowest portion of the curve contain from 60 to 70 

 per cent, of silver. The results are interesting, as they show 

 that the curves of fusibility and electric conductivity are very 

 similar. 



Mr. Roberts then describes experiments in which alloys were 

 cast in red-hot moulds of firebrick, the metal (about 50 oz.) 

 being slowly and uniformly cooled. The results of these experi- 

 ments on liquation are elaborate, and cannot be given in a brief 

 abstract. 



The density of pure silver and of Levol's homogeneous alloy, 

 while in the fluid state, were then determined by the method 

 described by Mr. Robert Mallet,* the metals being cast in 

 conical vessels of wrought iron. The results obtained were as 



follows ; 



Pure silver 

 Levol's alloy 



lensity fluid. Density st 



9-4612 10-57 



9-0554 9-9045 



In the case of silver, the mean linear expansion deduced from 

 this change of density is 00003721 per i°C,, which is nearly 

 douple the coefiicient at temperatures below 100° C. 



Physical Society, March 13.— Dr. J. H. Gladstone, F.R.S., 

 president, in the chair. — Mr. W. Chandler Roberts read a paper 

 on the electro-deposition of iron. He referred to the beautiful 

 specimens of electro-iron, the work of M. Eugene Klein, a dis- 

 tinguished Russian engineer and chemist, which were exhibited 

 at the meeting of the British Association at Exeter. In 1870 Mr. 

 Roberts visited St. Petersburg, and had the advantage of receiv- 

 ing from the late M. de Jacobi suggestions which enabled him to 

 deposit iron with much success. He stated that a plate of 

 electro-iron 150 mm. square by 2 mm. thick, was deposited on 

 copper, by Herr Bockbushmann, in 1846. In 1857, M. Feuquieres 

 exhibited specimens of electro-iron at the Paris Exhibition. In 

 1858, M. Gamier patented in England his process, termed 

 aeii'ia^e, for protecting the surfaces of engraved copper-plates ; 

 and in the same year Klein produced the admirable works above 

 referred to. The author then exhibited specimens which he had 

 obtained by Klein's method. The bath consists of a double 

 sulphate of iron and magnesia, of sp. gr. I'I55 ; '1^^ chief con- 

 ditions of success bt-ing the neutiaUty of the bath and the em- 

 ployment of a very feeble current. Iron so obtained possesses a 

 higher conductivity than any commercial iron (Matthiessen), its 

 sp. gr. is 8'139, and its occludes thirteen times its volume of hy- 

 drogen. A tube of the metal deposited on a rod of wax, which was 

 vacuum-tight at the ordinary tem.peiature, allowed hydrogen to 

 pass freely at a dull red heat. — After a brief discussion, Prof 

 Guthrie described some experiments which he has recently made, 

 with the assistance of Mr. R. Cowper, in continuation of former 

 researches, on salt solutions and attached water. The main 

 object of these experiments was to ascertain the manner in which 

 mixtiirts of salts act as cryogens, and to study their combination 

 ' Prgg. Roy. Stc, vol. x.\iii. p. 2C9. 



