f 



December 23, 1897J 



NA TURE 



189 



people of the country. Technical education was necessary. He 

 was not one of those who could see for a moment that the pros- 

 perity of England was on the wane. But if England meant to 

 keep her position in the commercial world she must not be be- 

 hind with regard to the most important thing which had arisen 

 in modern days connected with commerce — namely, the necessity 

 of giving technical instruction to those who had to work in 

 England's commercial market. 



SCIENTIFIC SERIALS. 



Anterican fournal of Science, December. — A microsclerometer, 

 for determining the hardness of minerals, by T. A. Jaggar. 

 This instrument depends upon the energy required to make a 

 boring of a certain diameter and depth under a given weight and 

 by means of a diamond point of a cleavage tetrahedron of perfect 

 shape. The hardness is measured by the number of turns re- 

 quired to make the boring, or by the depth reached after a 

 certain number of revolutions. The depth is measured by a 

 microscope attached to the boring point, by bringing successive 

 divisions of a slanting micrometer scale into focus. The values 

 found for the hardness of Mohs's scale-minerals show even greater 

 gaps than those obtained by Pfafif and Rosival. Taking corun- 

 dum as 1000, topaz is 152, quartz 40, orthoclase 25, apatite 

 I "23, fluorite 075, calcite 0*26, and gypsum 0"04. — On the 

 sapphires from Montana, by G. F. Kunz. Sapphires were first 

 found in transported gravels along the bars of the Upper 

 -Missouri, then in the earthy products of decomposed dikes, and 

 lastly further down in the unaltered igneous rock itself Much 

 beautiful material has already been obtained, but little of high 

 value. — On the corundum-bearing rock from Yogo Gulch, 

 Montana, by L. V. Pirsson. The dikes of-igneous rock con- 

 taining sapphire and corundum are of a dark grey, basic ap- 

 pearance, and have an uneven fracture. In thin sections it 

 a]3pears as a dark lamprophyre, consisting mainly of biotite and 

 pyroxene. There is a little iron ore present, but much less than 

 is usually seen in rocks of this class. — Electrical measurements 

 by alternating currents, by Henry A. Rowland.' Gives some 

 twenty-foAir methods of measuring inductances, capacities and 

 resistances by means of alternating currents. Some of these 

 depend upon a new principle in the shape of an adjustment of 

 two currents to a phase difference of 90°. This is done by passing 

 one current through the fixed, and the other through the suspended 

 coil of an electrodynamometer. The fixed coil may then be 

 made to carry a heavy current, and the sensitiveness of the ap- 

 paratus is greatly increased. Inductances can be compared to 

 within I in to,ooo, but care must be taken not to twist the 

 leads, as their electrostatic action is then very great. The 

 question of standard inductances is thus practically solved. 



The latest issue of the Izvestia of the Russian Geographical 

 Society is of exceptional interest. It contains, first, a brief 

 sketch, by P. K. Kozloff, of the Roborovsky's Tibet expedition, 

 i n which the author dwells especially upon his own " excursions " — 

 that is, the journeys which he made separately from the main body 

 of the expedition, and gives very valuable data relative to the 

 nature, and especially the animal world, of the visited regions. 

 The reports about the journey in the Sy-chuan province, and to 

 the Southern Kukunor ridge are especially interesting. — The 

 , geologist, E. E. Anert, contributes a very valuable sketch of his 

 journeys in Manchuria. He started from the Suifun river, near 

 Vladivostok, and went first to Ninguta, and then to Ghirin, the 

 capital of Manchuria, where he took a boat and went down the 

 Sungari till its junction with the Amur. The great Manchurian 

 ij river, up to Ghirin, has been described already in 1864, by the 

 1 1 expedition of Colonel Chernyaeflf, who had with him the astro- 

 , I nomer Usoltseff and P. Kropotkin ; but the papers of these two 

 ■ I explorers, which were printed in the Memoirs of the Siberian 

 Geographical Society, were destroyed, as well as the original 

 maps, during the Irkutsk conflagration, and remained almost quite 

 unknown to geographers. — A third paper, of great interest, is by 

 V. I. Lipsky, who was the leader of the Hissar expedition of 

 1896. Notwithstanding great difficulties, due to heavy snow- 

 falls in winter, which were followed by heavy rains in spring, 

 Lipsky explored the Hissar ridge from the south. The heights of 

 J the passes are from 12,000 to 14,000 feet. Ten new glaciers were 

 discovered ; they all lie above the 10,000 feet level, and are all 

 surrounded by large moraines testifying to their previous larger 

 extension. — The fourth paper is by Th. K. Drizhenko, who was 



NO. 1469. VOL. 57] 



at the head of a hydrographic expedition for the exploration of 

 Lake Baikal in 1896. The paper is accompanied by a map of 

 the lake showing the positions of the 100, 400 and 700 fathoms 

 depth-lines, and another map showing the distribution of .surface 

 temperature during the month of August. The work of the 

 expedition was continued this summer as well. — In the same 

 issue G. V. Levitsky discusses the advisability of having a few 

 seismic observatories in Siberia and Central Asia, each provided 

 with a horizontal pendulum. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, December 9.—" On the Refractivities of 

 Air, Oxygen, Nitrogen, Argon. Hydrogen, and Helium." By 

 Prof. William Ramsay, LL.D., F.R.S., and Morris W. 

 Travers, B.Sc. 



In the course of an investigation on the nature of helium, 

 many measurements of the refractivities of different samples 

 were made with a view to determining their composition. 



Since, on account of the great difference between the refrac- 

 tivities of air and helium, it was found inconvenient to compare 

 the two gases directly, the helium was compared with hydrogen, 

 and the refractivily of the hydrogen was afterwards determined 

 with regard to air. As a check the hydrogen was subsequently 

 compared with oxygen, and nitrogen free from argon, these gases 

 were also measured against one another, and against air. At a 

 later stage in the investigation the refractivities of argon and 

 carbon dioxide were also determined. 



The measurements were made by the interference method 

 described by Lord Rayleigh (Proc. Roy. Soc, 59, 198-208). 



Special attention was paid to the purity of the gases examined, 

 and a full description of the methods of preparation is given in 

 the paper. It is possible that the discrepancies between the re- 

 sults obtained by various observers may be due to the presence 

 of impurities in the gases which they employed. 



The mean values obtained for the refractivities of the gases . 

 examined are tabulated below. 



Refractivities of Gases, Air equal to Unity. 



Through 



Calculated from the determinations given above, assuming 

 Dale and Gladstone's formula for mixtures of gases, the refrac- 

 tivity of air becomes 99*647 instead of 100. 



Turning to the determinations of other investigators, it was 

 found that since Dulong, in 1826, no single experimenter had 

 made measurements of both oxygen and atmospheric nitrogen. 

 Mascart determined the refractivily of nitrogen, and found it to 

 be 1-0178, a value which closely agrees with the figure given 

 above. 



Lorenz determined the value for oxygen, 0-9347, but there is 

 reason to doubt the purity of the gas which he employed. The 

 refractivity of air calculated from the data of Mascart and. 

 Lorenz becomes ioo'i5. 



Since the value obtained for the refractivity of air, calculated 

 from the values obtained for oxygen, nitrogen and argon, differs- 

 from 100 by an amount far exceeding the limit of experimental 

 error, we were driven to the conclusion that the refractivity of 

 air is somewhat less than the refractivities of its constituents, 

 taken in the proportion in which they occur. 



It appeared advisable to try other mixtures ; and a mixture of 

 hydrogen and helium was first selected, because these are both 

 very "perfect" gases, inasmuch as their critical points lie very 

 low. It was to be expected that if a difference between 

 calculated and found values should exist, it should be of the 

 inverse character to that of a mixture of oxygen and nitrogen, 

 for they are two somewhat " imperfect" gases. The result has 

 borne out this idea. 



A mixture was made of 2060 c.c. of hydrogen and of 

 20-I2 c.c. of helium free from argon, and of the density 1-960 ; 

 and with the refractivity of the mixture those of hydrogen and 



