248 



NATURE 



[December 22, 1910 



The use of the Clark and Weston cells as standards of 

 «lectronniOtive force has necessitated a close study of the 

 properties of cadmium and zinc amalgams, and numerous 

 valuable papers on this subject have issued from the 

 van 't Hoff laboratory at Utrecht. In the current number 

 of the Zeitschrift fiir physikalische Chemie (December 2) 

 is a further contribution from this laboratory by Ernst 

 Cohen and P. J. H. van Ginneken, dealing with the 

 properties of zinc amalgam as affecting the Clark cell. 

 The authors conclude that the formula in current use 

 representing the relation between the E.M.F. and the 

 temperature of the Clark cell is not trustworthy, and 

 should not be employed in accurate measurements. It is 

 further shown that for e.xact work the Clark cell must be 

 used at temperatures between 20° C. and 38° C. 



The Department of Mines, Canada, has sent us a copy 

 of the report of analyses of ores, fuels, &c., made in the 

 chemical laboratories of the Geological Survey during 

 1906 and 1907, and of the Mines Branch of the Depart- 

 ment of Mines in 1906, 1907, and 1908. With the excep- 

 tion of twenty-seven rock analyses, the work done is 

 chiefly of practical interest, analyses being given of 

 numerous coals, lignites, peats, and ores of iron, copper, 

 and chromium. The results of seventy-seven gold and 

 silver assays show the wide distribution of the precious 

 metals in Canada. In an appendix a description is given 

 of the commercial methods and apparatus used for the 

 analysis of oil-shales. 



Messrs. Whitcombe and Tombs, Ltd., will publish 

 shortly a fully illustrated work on " Australian Plants " 

 ■suitable for gardens, parks, timber reserves, &c., by Mr. 

 W. B. Guilfoyie. 



OUR ASTRONOMICAL COLUMN. 



A Projection on Saturn's Outer Ring. — During the 

 total eclipse of the moon on November 16 M. Jonckheere 

 directed the 35-cm. equatorial of the Hem Observatory to 

 Saturn, and found a bright projection extending outwards 

 from the eastern extremitj- of the exterior ring. The 

 projection was best seen with low jxjwers (100 and 200), 

 and its intensity decreased gradually, going from the 

 outer edge of ring A on to the background of the sky. 

 On November 20 and 24 the same projection was seen 

 with difficulty (Astronomische Nachrichten, No. 4461). 



Discovery of Another Nova, Sagittarii No. 3. — In a 

 note appearing in No. 4459 of the Astratiomische Nach- 

 richten Prof. E. C. Pickering states that Miss Cannon 

 has found that a new star appeared in the constellation 

 .Sagittarius on August 10, 1899. A photograph taken on 

 August 9, although showing stars of magnitude 11-5 in 

 the immediate neighbourhood of the nova, shows no trace 

 of it, yet on August 10 it is a conspicuous object of magni- 

 tude 8-5. While the outburst v/as so sudden, the decline, 

 as is common with such objects, was very rapid, for the 

 light faded from 8-6 on August 25 to 10-5 on October 13, 

 1899 ) the decrease after that date was more gradual. 

 The nova is not shown on any photograph taken after 

 October, 1901, when its magnitude was about 13-0. The 

 position of this object was R.A. = i8h. i2-2m., dec. = — 

 25° 14' (1875-0) ; this is about lom. west of A. Sagittarii 

 and 20m. east of Nova Sagittarii No. 2. 



Faye's Comet. — Having identified Cerulli's comet with 

 Faye's short-period comet, M. G. Fayet has investigated 

 the orbit with the idea of obtaining closer agreement with 

 Dr. Stromgren's elements. Employing three observations, 

 made between November 10 and 22, he calculated the value 

 for the mean motion and obtained two sets of elements, 

 which, however, were not altogether satisfactory. Then 

 on November 30 he secured a further observation, and this 

 enabled him to apply the method of the variation of geo- 

 centric distances and to calculate other systems, the fifth 

 of which agrees very nearly with Dr. Stromgren's elements 

 for 1903, except that the mean motion is 486-792" instead 



NO. 2147, VOL. 85] 



of 480-16"; they also give a close agreement with the 

 observations. From the best system obtained, which may, 

 however, yet be improved, M. Fayet has calculated an 

 ephemeris giving daily positions up to January 30, 1911 

 (Astronomische Nachrichten, No. 4461). 



New Experimental Demonstration of the Earth's 

 Rotation. — ^An interesting description of an experiment 

 devised by Father Hagen to demonstrate the rotation of 

 the earth is described by M. B. Latour in No. 1346 of 

 Cosmos (November 12). Father Hagen 's apparatus 

 consists of a balanced beam of wood, 9 metres long, which 

 has a bifilar suspension, and to which is attached heavv 

 masses movable in the horizontal plane towards and awav 

 from the suspension. In the modified experiment these 

 masses each consist of 80 kilograms of lead mounted in 

 small waggons, which can be automatically released by 

 the fusion of a leaden wire. When released the w.iggons 

 run towards the centre, the moment of inertia of the beam 

 is modified, and it swings relatively to the earth ; the 

 motion is shown by a mirror attached to the suspension 

 and reflecting a beam of light on to a scale fixed on the 

 wall of the circular room wherein the apparatus is in- 

 stalled. When the chariots are made to run from iIt- 

 centre to the extremities the swing of the beam is in the 

 opposite direction and about half the amount. W'ith 

 Father Hagen 's apparatus, mounted in the massive tower 

 which carries the astrographic equatorial at the Vatican 

 Observatory, the mean of twenty experiments gave a value 

 for the earth's rotation very near the theoretical value at 

 Rome. 



Investigation of the Orbit of ^^'oLF's Comet, 1898- 

 191 1. — In No. 4460 of the Astronomische Nachrichten 

 M. M. Kamensky gives in brief the results of an elaborate 

 investigation he has made of the movements of Wolf's 

 comet during the period 1898-19 11. This is the well- 

 known short-period (6-7 years) comet discovered by Wolf 

 at Heidelberg on September 17, 1884, and independently 

 by Copeland with the spectroscope on September 22 ; it 

 was reobserved in 189 1 and 1898, but was not seen in 

 1904-5. The orbit was completely transformed by Jupiter 

 in 1875, but the slight differences between the observed and 

 calculated places in 1898 indicate that it is now a per- 

 manent member of our system. 



M. Kamensky first investigated the motion during the 

 period 1898 August 22 to 1904 June 12, taking into 

 account the perturbations of the earth. Mars, Jupiter, 

 Saturn, and these are published in full in No. 15 (1910) 

 of the Bulletin de I' Academic linperiale des Sciences de 

 St. Petersbourg. He then carried the investigation for- 

 ward to March 28, igii, and publishes the full tables in 

 No. 16 of the Bulletin ; he also gives elements showing 

 the severe perturbation by Jupiter in 1875, and states that 

 extraordinary changes may again take place at a near 

 approach in the latter part of 1922. 



According to the final elements, the next perihelion 

 passage should occur on February 24, 19 12, and in Bulletin 

 No. 16 M. Kamensky gives an ephemeris for the period 

 191 1 January 3 to October 14; for the latter date the 

 estimated magnitude is 12-2. 



The Light Changes of Forty-nine Variable Stars.— 

 In the fourteenth issue of the Bulletin International, pub- | 

 lished by the Cracow Academy of Sciences, Dr. L. Pracka i 

 discusses the light changes of forty-nine variable stars. 1 

 The observations were made at the Bamberg Observatory ( 

 during 1905-9, and each star is discussed at length. A 

 summary of the results is given in handy tabular form at j 

 the end of the paper showing the elements, the magni- 

 tudes and colour, and the form of the light-curve for each I 

 object. I 



THE PHYSICAL SOCIETY'S EXHIBITION. 



(~)^ Tuesday, December 20, the Physical Society of 

 ^^^ London held its annual exhibition of physical | 

 apparatus, and the occasion was marked by some interest- ; 

 ing experimental lectures. Prof. J. A. Fleming, F.R.S., 

 chose for his subject some improvements in transmitters j 

 and receivers for wireless telegraphy, and referred first 

 to his well-known oscillation valve, consisting of a gloW i 

 lamp in which a metal plate of some convenient form is ,. 



