

NA TURE 



[Januarv 31, 1895 



the restoration of isos'atic equilibrium is attended by minor 

 oscillaMons, the conditions requisite for repose having been 

 OTerpassed by the early rei.levation of outer portions of each o( 

 these great glaciated areas. The close of the Ice Age was not 

 long ago, geologically speaking, for equilibrium of the disturbed 

 areas h.^s not yet been restored. — .\n automatic mercury vacuum 

 pump, by M. I. Pupin. This pump is a combination of a suction 

 pairp capable of raising mercury to practically any height, and 

 an ordinary Sprengel pump, the two being connected by a 

 siphon barometer Mercury is pumped into the Sprengel 

 reservoir by the suction pump. The reservoir of the latter is 

 provided with two vertical tubes dipping into two mercury 

 vessels. The end of ore of these is higher than that of the 

 other, so that when the mercury has fallen to the level of ihe 

 end, no more mercury enters the tube, and the column already 

 in it is bodily drawn up into the siphon barometer. — Graphical 

 tfaermodyoimics, by Rene dc Saussure. The author recom- 

 mends the adoption of new coordinates inste.-id of P and V. 

 Instead of these, he advocates the variables ip and s, defined by 

 the equations ^ = t'»"-' and s = xa-, where i is the period and 

 a the amplitude of the vibratory motion constituting heat. 

 Then the value of each variable depending upon the phenomenon 

 can be obtained graphically. — Solutions of salts in organic 

 liquids, by C. E. Lincbarger. 1 he law enunciated by Schroeder 

 and Le Chatelier, that the solubilities at equal intervals from 

 the temperature of fusion for different solid bodies and in 

 difTerent solvents are the same, although approximately true 

 for the cases investigated by them, is not applicable to the case 

 of inorganic salts in normal organic solvents. 



Wifiirmaiin's Aiirialen der Physik und Chemie, No. 13, 

 1894. — A new spectrum photometer, by Arthur Kimig. 

 Between the telescope and the collimator, which is provided 

 with two parallel slits, are introduced, besides the refracting 

 flint-glass prism, a twin prism and a Rochon polarising prism. 

 One of the slits is provided with a total-reflection prism, in 

 order to admit Ihe standard light from the side. The iield of 

 vie* shows two semicircles, one for each of the sources of 

 light, and their relative intensities can be adjusted and 

 measured by a Nicoll prism near Ihe eye. The observer notes 

 the angle through which the Nicoll prism must be 

 rotated in order to give equal intensities to the two halves of 

 the field.— Spectra of various sources of light, by Else 

 Kotigen. By means of K'^nig's spectrum photometer, various 

 petroleum and gas lamps were spectroscopieally studied. — On 

 the process of light emission, by G. Jaumann. The author 

 shows that the emissive vibrations of a luminous body exhibit 

 a damping which maybe measured — Capillary electrometers 

 and drop electrodes, by G. Meyer. The surface tension of 

 mercury and some, but not all, amalgams is reduced by the 

 addition of a solution of a salt of mercury, or of a salt of the 

 metal contained in the amalgam. The reduction of .surface 

 tension which takes place during anodic polarisation is due to 

 the formation of such mercuric or metallic salts. — Thermo- 

 electricity of chemically pure metals, by K. Noll. This paper 

 gives an account of a careful redetermination of the thermo- 

 electric forces of pure Cd, Sn, Ag, Au, Cu, Zn, Al, Pt, Mg, Fe, 

 Ni, Hg, and German silver. — Influence of magnetisation and 

 lemperaiure upon the eltctric conductivity of bismuth, by J. B. 

 Henderson. The author shows that, before bismuth spirals 

 can be employed to measure magnetic fields by their change of 

 resi<tance, it will be necessary to lind a ready me.ins of testing 

 their temperature, as the resistance is profoundly affected by 

 change in the latter. — High temperature thermometers of Jena 

 glass .N'o. 59'!' , by .\lfons .Mahlke. These thermometers have 

 to be filled partly with liquid carbonic acid, after which they 

 maybe employed for temperatures up to 550, the carbonic 

 acid keeping the mercury from boiling. The author dcfcribes 

 how he found the expansion of the glass and Ihe mercury (or 

 such high temperatures, and calibrated one of the thermo. 

 meters with reference to the air thermometer. 



Bulliiin de la Sini/ti dt> Natural! ltd de Afoscoit, 1894, No. 

 I. — Contributions to the Moss flora of Russia, by iJr. Ernst 

 /ickcndratb, being an enumeration of 202 species collected by 

 Ihe author in European Russia proper (in German) — The 

 formation of the primary blastoderms and the origin of Ihe 

 chord and the mesoderm in the Vertebrates, by H I^wolT (in 

 German, with sis plale«). A work which alieady has been 

 partially published in Hiolo^iichei CrnlralHatt for 1892 ; it is 

 based on the study of the embryology of the Amphioxiis, 



NO. 13 18, Vr.L. 51 ] 



the Pttromyzon, the Axolotl, the Pristinrus and Torpedo, 

 several fishes and the I.aceria, an 1 the author comes to the 

 conclusion that the whole of the process is quite difi'erent from 

 what is usually described as gastrulation. The paper is to be 

 continued. — .A. general expression of the Thermodynamic 

 Potential, by N. OumotT. — -Meteorological observations at 

 the Petrovak .Agricultural .\cademy for the year 1893. 



SOCIETIES AND ACADEMIES. 



London. 



Royal Society, January 17. — "The Latent Heat of 

 F.v.iporaiion of Water." By E. H. Griffiths, M..\., Sidney 

 Sussex Collet;e, Cambridge. 



.\ calorimeter was suspended within a chamber the walls of 

 which were kept at a constant temperature in the manner 

 described in a previous paper.' The calorimeter was filled 

 with a singulaily limpid oil, which was stirred by paddles 

 revolving about 320 times per minute, and immersed in the 

 oil was a silver flask, which contained the water to be evaporated. 

 The ends of a platinum-silver coil, within the calorimeter, were 

 maintained at a known constant poiential difierence, and the 

 rate of evaporation so controlled as to exactly balance the heat 

 supplied by the electric current. The advantages of this 

 method are that the results are not appreciably afTected by 

 (1) eirors in thermometry ; (2) changes in the specific heat of 

 water ; (3) errors in the determination of the water equivalent ; 

 (4) loss or gain by convection, &c. DitTcreniial platinum- 

 thermometers were used, in order to ascertain the equality of 

 Ihe calorimeter temperature and th.Tt of the surrounding walls, 

 thus differences of 00004° C. eould be accurately measured, 

 and smaller differences detected. - 



A series ol experiments in which the saturated vapour was 

 removed from the flask by a stream of dry gas, gave the following 

 results. 



Temp. (Nitrogeo L (in terms of a therm.tl 



Scale). unit at i;,^). 



24"-96 5819 



39 '99 5724 



49"'82 5'>6 5 



The method of experiment was then altered ; rapid evapora- 

 tion was caused by removal of pressure, and the mass of water 

 evaporated determined in a different manner. 



A considerable number of experiments gave the following 

 results. 



Temp. (N. Scale). Extreme values of L. Mean I,. 



30^00 ... 578 58 - 5/8 90 ... 578 70 

 4o'''i5 ... 572-12 - S73'oi ... 572-60 



The conditions as to rate of evaporation, &c., were varied 

 greatly during the experiments. 



The results are expressed by the following formula : 



L = 59673 - 0-60109 



This formula would give 



L = 596-73 when 9 = o 

 and L = 53663 ,, « = 100°. 



.\nd these values are aim 1st identical with those obtained by 

 Uielerici at o' (596-73) and Regn.iult at 100 (536 60). A study 

 of the results leads the author to the conclusion th.-it Ihe 

 " thermal unit at 15° " must be almost identical with the " mean 

 thermal unit between 0° and 100." It has been shown by 

 Rowland, by Itartoli and Stracciati, and by the author, that at 

 low temperatures the specific heat of water decreases as the 

 temperature rises, and it is proha'<Ie that it arrives at a minimum 

 between 30 and 40°, afterwards increasing with rise of tem- 

 perature. There is, therefore, nothing impossible in the above 

 supposition. 



An investigation into the density of aqueous vapour 

 (assuming the author's values of I. and J) indicates that at 

 low pressure- the density of the saluratc<l vapour is that of a 

 perfect gas, and that at higher pressures (above 140 m.m.) it 

 attains a density about I -02 times as great as the "theoretical 

 dt nsily." 



January 24. — ^" Malhemalical Contributions to the Theory of 

 Evolution. II. .Skew Variation in Homogeneous Material. " By 

 Prof. Karl Pearson, University College, London. (Seep. 3'9)' 



I ''The Mccfianical Kquivalent,' Phil. Trans. 1893 A, pp. 361-504. 

 '-■ Sec Phit. Mat;. January 1895. 



1 



