-» r -> 



NA TUKE 



[February 12, 1903 



students with an elementary treatment of rigid dynamics, 

 and was reviewed in Nature of May 5, 1892 (vol. xlvi. p. 4), 

 has so successfully fulfilled its purpose that it is now in its 

 fourth edition. In this edition the author directs special 

 attention to the use of the " inertia skeleton," in which a 

 body is replaced by a dynamically equivalent system of three- 

 thin wires placed along the three principal axes at its centre 

 of mass. This method of representation has been found to 

 appeal to non-mathematical students far better than the con- 

 ventional momental ellipsoid. Further attention has also 

 been given to experiments with a gyroscope, which are so 

 easily made that it is a matter for congratulation that they 

 can now be studied in an elementary treatise. The author 

 introduces the name " slug " to denote the mass to which 

 a foot-pound unit of acceleration is produced by a gravita- 

 tion unit of force. 



According to recent investigations, liquid sulphur dioxide 

 is a solvent in which a large number of substances, oiganic and 

 inorganic, are readily soluble. From experiments of VValden 

 and Cenmerszwer, published in the Zeilschrift fiir physikalische 

 Chemie, it appears that sulphur dioxide forms complex com- 

 pounds with many of these substances From solutions of 

 potassium iodide in liquid sulphur dioxide, they have obtained 

 a crystalline compound of the formula KI.4SO.,, which melts at 

 + 0, 26 C. Similar compounds are in all probability formed 

 by other salts, and the name of " sulphones " is ascribed to 

 this class of bodies. 



In the current number of the Zeitschrift fiir physikalische 

 Chemie is a noteworthy paper by Messrs. Alexander Smith and 

 W. B. Holmes in which the nature of amorphous sulphur is 

 discussed. This so-called amorphous sulphur is formed when 

 liquid sulphur is maintained in the molten condition for s ime 

 time, and its amount increases as the temperature is raised. A 

 method of determining the proportion of amorphous sulphur in 

 the liquid variety has been worked out which depends essentially 

 on the great difference in solubility of the two forms in carbon 

 bisulphide. From parallel determimtions of the proportion of 

 amorphous sulphur and of the freezing point of the melt, it is 

 shown that the lowering of the freezing point below 119 "■25 C. 

 is proportional to the quintity of the dissolved amorphous 

 sulphur. The molecule of the latter in the solution of the 

 soluble liquid form is found to be represented by the formula 

 S s . 



A new reducing agent which promises to be of consider- 

 able service is described by Mr. E. Knecht in the current 

 number of the Berichte. From the analogy between titanium 

 and tin, it appeared likely that the chloride of titanium on 

 reduction would give a lower chloride TiCl,, analogous 'o 

 stannous chloride. The reduction of the acid solution of the 

 tetrachloride of titanium, however, produced the trichloride 

 already known instead of the expected dichloride, but this, 

 on examination, proved to possess remarkable reducing 

 properties. Whilst applicable to reduction in a similar 

 manner to stannous chloride, titanium trichloride is more 

 powerful. Copper salts can be reduced to metallic copper ; 

 sulphites may be quantitatively reduced to hyposulphites, 

 or, if the action be pushed, sulphur is produced. By careful 

 neutralisation with soda, the titanium can be completely 

 removed as the hydrated oxide. The behaviour of titanium 

 trichloride towards organic substances is also of interest ; 

 nitro-bodies are reduced immediately to amines, and in the 

 case of substances containing more than one nitro group, 

 the partial reduction is readily effected. Azo-bodies are 

 attacked so sharply that they may be quantitatively estim- 

 ated, and other reactions are given showing the wide range 

 of applicability of this reagent. 



NO. 1737, VOL. 67] 



Some time ago it was shown by M. C. E. Guillaume that 

 it was possible to obtain nickel steel alloys which possessed 

 extremely low coefficients of expansion, and in the current 

 number of the Comptes rendus he gives a more detailed 

 study of the conditions necessary to obtain such alloys. The 

 expansion is influenced considerably by the presence of 

 foreign elements such as manganese, carbon and silicon, 

 and it has been found that if these are reduced below a 

 certain amount, the alloy cannot be worked. Working under 

 the most favourable conditions, an alloy has been obtained 

 po sessing a coefficient of expansion a = ( + 002S -o 002326) io _fi , 

 a figure which can be better understood when it is stated 

 that a wire made of this steel, one kilometre in length, 

 would alter in length in passing from o° to 20 C. less than 

 o'4 mm. The importance of an alloy possessing such pro- 

 perties in geodetic work is obvious, and extensive use has 

 already been made of it in the geographical service of the 

 French armv, in the marine hydrographical service and 

 elsewhere. All temperature corrections in geodetic work 

 become superfluous. 



The additions to the Zoological Society's Gardens during 

 the past week include a Barnard's Parrakeet (Platycercus 

 ■ barnardi) from Australia, presented by Mrs. Jebb ; a Haw- 

 | finch (Coccothraustes vulgaris), British, presented by Miss 

 H. Brown; a Rufous Rat-Kangaroo (Aipyprymnus ruje%- 

 1 . in 1 from New South Wales ; two Corean Cattle (Bos taunts, 

 var.) from Corea, six Proteus (Proteus anguinus) from the 

 Caves of Carniola, deposited. 



OUR ASTRONOMICAL COLUMN. 

 Elements and Ephemeris of Comet 1903 a. — The 

 following elements and ephemeris for this comet have been 

 calculated, by M. G. Fajel, of Paris Observatory, from observ- 

 ations made at Nice (January 19), Besancon (January 24) and 

 Paris (M. Bigourdar, January 27) ; the necessary corrections for 

 aberration and parallax have been made. 



1903 March 28-9468 M.T. Paris. 



w = 130 40 55] 

 fl = 041 56-1903-0 

 i = 35 35 6j 

 log q = 9'b7-479 



Ephemeris 12/1. M.T. Tan's, 

 Date. a app. 5 app. log r 



Feb. 9 

 15 

 '7 



21 



25 



log Ji Brigbt- 

 h. m. s. „ , ness. 



23 24 50 +8 7-1 00619 0-2517 2'I 



2331 17 + 927-7 OO348 02395 2'5 

 23 38 



jS t6 +10537 00056 02257 31 



=3 45 49 +1225-1 99742 o-2ioi 3-8 



23 54 3 +H 25 99403 0-1923 4-8 



March 1 032 -+ 15 455 99039 o 1721 6-3 



The brightness on January 19 (about 10m. 0-1 im.'o) is 

 taken as unity (Astronomische Nachriehten, No. 3S45). 



The Constant of Aberration and the Solar 

 Parallax. — In No. 529 of the Astronomical Journal, Dr. 

 Chandler gives the results of an exhaustive inquiry, which he 

 has conducted during the last ten years, into the various values 

 obtained for the constant of aberration by different observers and 

 methods. After discussing the trustworthiness of the methods 

 employed, Dr. Chandler apportions various weights to the results 

 obtained, and then rejects a number of these results as being 

 too uncertain. He then determines the constant from the 

 accepted results, and obtains, as the general mean, the value 

 2o"'52t with a probable error of + o" 005. 



In order to show the effect of incorporating all the results, he 

 determines the weighted mean of all the values and thereby 

 obtains the value 20" 5 1 7. 



As a final result ot the inquiry, Dr. Chandler accepts the 

 value of 2o"'52 for the constant of aberration, and this produces 

 the value 8" 78 for the solar parallax. 



A New Form of Spectroscope. — In No. 12, vol. xxxi., 



