Dec. 19, 1889] 



NATURE 



167- 



such heatings and cooHngs the temperature coefficient of iron 

 could be brought down to something approaching the number 

 given by Matthiessen for " most pure metals." The wire experi- 

 mented on was first annealed by heating to 1000° C. for several 

 hours and allowing to cool slowly in a furnace placed at right 

 angles to the magnetic meridian ; the process was repeated three 

 times. Afterwards the wire was covered with paper and wound 

 doubly into a coil. This coil was inclosed in a water-jacketed 

 air-chamber, and connected with a sensitive Wheatstone bridge. 

 Thermo-electric and Peltier effects were eliminated by always 

 keeping the galvanometer circuit closed. By repeated heating 

 to 100° C. and cooling to 17° C. for long intervals, the specific 

 resistance at 17° C. was reduced from 11,162 to 10,688 

 C.G. S. units, after which the operations produced no further 

 change. At the same time the temperature coefficient in- 

 creased in the proportion of I : i "024. From careful determina- 

 tions of the resistance at different temperatures, the formula 

 R/ = Rj(i + 0-005131/ + o-ooooo8i5/'-) was deduced, whilst that 

 obtained from Matthiessen's results for pure iron annealed in hy- 

 drogen is R/=R|,(i -1-0 005425/ -fo-ooooo83/-). Taking his own 

 determination of specific resistance of impure iron as correct, 

 coupled with Matthiessen's law connecting the resistances and 

 temperature coefficients of metals and their alloys, the author 

 finds that the specific resistance of pure iron deduced from 

 Matthiessen's results is from 4 to 5 per cent, too high. In con- 

 clusion, Mr. Tomlinson expresses a hope that the B.A. Electrical 

 Standards Committee may be induced to determine the absolute 

 resistance and temperature coefficient of the pure metals which 

 are in ordinary use. Prof. Ayrton thought Matthiessen's results 

 were expressed in B.A. units, and hence might appear i or 2 

 per cent, too great. Mr. Tomlinson, however, believed the 

 number he took were expressed in legal ohms. Dr. Walmsley 

 asked for what value of the magnetizing force the permeability of 

 the iron mentioned in the beginning of the paper was determined ; 

 to which Mr. Tomlinson replied that they were much smaller 

 than the earth's horizontal component. — Dr. Thompson's paper 

 on geometrical optics was postponed. 



Edinburgh. 



Royal Society, December 2. — Sir Douglas Maclagan, Vice- 

 President, in the chair. — Prof. Tait communicated a paper by 

 Dr. G. Plarr, on the transformation of Laplace's coefficients. — 

 Mr. A. C. Mitchell read a preliminary note on the thermal con- 

 ductivity of aluminium. A comparatively rough first experiment 

 shows that this metal slightly exceeds good copper in conduc- 

 ductivity. — Dr. John Murray discussed the question of the origin 

 and nature of coral reefs and other carbonate of lime formations 

 in recent seas. He first referred to experiments which have 

 recently been made regarding secretion and solution of carbonate 

 of lime. Carbonate of lime remains are found in great abund- 

 ance at the sea bottom in shallow waters, but the amount 

 steadily diminishes as the depth increases, until at 4000 fathoms 

 almost every trace has disappeared. This is due to solution, as 

 the organisms slowly fall to the bottom. Everywhere within 

 500 fathoms of the surface the ocean teems with life. The 

 Greely Expedition was starving within ten feet of abundant food 

 which might have been obtained by breaking a hole through the 

 ice and using a shirt as a drag-net. Dr. Murray then proceeded 

 to discuss his theory of the formation of coral reefs, bringing 

 forward in reply to objections by Dana and others, some recently 

 obtained facts regarding the existence of shallow regions in what 

 is, on the whole, deep water. He showed that carbonate of 

 lime is continually produced in great quantity in warm tropical 

 water by the action of sulphate of lime in solution on effete pro- 

 ducts. This explains the great growth of coral in tropical regions. 

 The absence of coral on certain shores in tropical districts is 

 explained by the uprise of cold water due to winds blowing off 

 shore. His paper was illustrated by an elaborate series of 

 lime-light diagrams. 



Paris. 

 Academy of Sciences, December 9. — M, Hermite in the 

 chair. — On the nitrification of ammonia, by M. Th. Schloesing. 

 In a recent communication (September 9) the author described 

 three experiments on the nitrification of ammonia in vegetable 

 humus, tending to prove that this phenomenon is accomplished 

 without any appreciable loss of nitrogen liberated in the gaseous 

 state. He now reports the results of two other experiments, 

 showing that this is no longer the case when a larger proportion 

 of ammonium carbonate is introduced into the soil. — Correction 



in the tables of Jupiter's movement worked out by Le Verrier,. 

 by M. A. Gaillot. Comparing the secular terms of the eccen- 

 tricity and perihelion of Jupiter's and Saturn's orbits as deter- 

 mined by Le Verrier, Hill {Astronotnica/ yournal. No. 204) 

 came to the conclusion that there must be an error of sign in the 

 terms of the second order relating to Jupiter's orbit. M. Gaillor 

 has now gone over the calculations again, and finds that Le 

 Verrier's manuscript is correct, but that, as conjectured by Hill, 

 a misprint of a sign occurs in the published work. In vol. x. 

 p. 242, the sign + appears instead of - before the term 

 o"'oi5>554'8' cos(a) - tt'). — On the characteristic temperatures,, 

 pressures, and volumes of bodies, by M. Ladislas Netanson. 

 These researches tend to show that for every gas there exists an 

 infinite number of characteristic values-, t, p, v, which, being 

 adopted as units of the general variables t, p, v, have the 

 remarkable property of eliminating all difference in the charac- 

 teristic equations of the different gases. The systems usually 

 employed in measuring temperatures, pressures, and volumes, 

 having nothing in common with the intimate nature of the bodies 

 themselves, give rise to differences in the equation F(/, /, v) = o, 

 which disappear when for each body the physicist employs a 

 special system in accordance with its properties. — On the localiza- 

 tion of the interference fringes in thin isotropic plates, by M. J. 

 Mace de Lepinay. In studying the exact conditions of the 

 fringes in thin prismatic plates, the author finds a complete 

 verification of the general theory expounded by him in 

 a previous communication (Comptes rendus, July 22, 1889). 

 The consequences of the theory may be considered as entirely 

 verified by these experiments. — On the want of accuracy in ther- 

 mometers, by M. E. Renou. On a recent occasion (July i) M. 

 Cornu remarked that hitherto these instruments have been liable 

 to an error of from o°'2 to o°'3. It is now shown that observa- 

 tions hitherto recorded may give rise to the greatest tincon- 

 venience, more perhaps in future than at present. These 

 remarks were supplemented by M. Cornu, who pointed out that 

 errors in the mercury thermometer as great as o°'2 or o°*3 occur 

 only in observations taken at considerable intervals of tempera- 

 ture and with instruments not sufficiently tested. — Variations in 

 the mean temperature of the air at Paris, by M. Renou. Twenty 

 years ago the author attempted to show that severe winters re- 

 turn in groups of five or six every forty-one years. This some- 

 what elastic period is perhaps reproduced better in groups of 

 years than in single years. It also appears that the Observatory 

 of Paris gives a mean temperature higher by o°7 than that of 

 the surrounding rural districts — 10° 7 as compared with 10° 'O of 

 the Pare Saint- Maur Observatory. — On the observations of tem- 

 perature on the top of the Eiffel Tower, by M. Alfred Angot. 

 I These observations, begun on July i, are being still continued 

 with a Richard registering thermometer, placed 336 metres 

 i above the sea, and about 301 above the ground. Compared with 

 j those of the Pare Saint-Maur (50 metres) they show that the 

 1 normal decrease of about 1° for every 180 metres is greatly ex- 

 ceeded in summer and during the day (means of the maxima), 

 and correspondingly diminished in winter and at night (means of 

 the minima) ; or there is generally even an inversion in the 

 temperatures, the air being then warmer at 300 metres than near 

 the ground. — Papers were submitted by M. Raoul Varet, on the- 

 ammoniacal cyanides of mercury ; by M. L. Prunier, on the 

 simultaneous quantitative analysis of sulphur and carbon in 

 substances containing sulphur; by M. E. Guinochet, on an acid 

 isomerous with tricarballylic acid ; by M. C. Tanret, on two new 

 sugars extracted from quebracho {Aspidosperina qjtebracho) ; by 

 M. Arnand, on carotine, its probable physiological action on the 

 leaf; and by MM. Andre Thil and Thouroude, on a micro- 

 graphic study of the woody tissues of native trees and shrubs, 

 prepared for the special exhibition of the Forest Department. — 

 The sealed paper, by M. A. Joannis, on compounds of potassium- 

 and sodium with ammonia gas, was opened by the Secretary. 



Berlin. 



Physical Society, November 22. — Prof, du Bois Reymond,. 

 President, in the chair. — Dr. Lehmann spoke on the nature and 

 distribution of the Babylonian metrical system. He expressed 

 his desire to lay before the competent judgment of the Physical 

 Society, the results of his most recent archaeological researches, 

 so far as they are of direct physical interest, and then proceeded 

 to describe the numerical system employed by the ancient 

 Baylonians, explaining that it consisted of a sexagesimal system 

 with decimal subdivisions. The imit of time, the double- 



