February 23, 191 1] 



NATURE 



55 



rain or hail, we must be able to cut off the supply of 

 moisture, or prevent rapid expansion. The most important 

 problem at the present time, and in future, will be to 

 attain a clear idea of the mechanics of the atmosphere as 

 a whole, comprised under the technical terms hydro- 

 mechanics, aero- and thermo-dynamics, and another century 

 may elapse before all these questions can be solved. 

 When meteorology has become more truly deductive, the 

 author further remarks, then we can pass to the satis- 

 factory discussion of the great problems that we now can 

 merely toy with. 



In an address delivered on December 29, 1910, as 

 retiring vice-president of Section B (Physics) of the 

 American Association for the Advancement of Science, Dr. 

 L. A. Bauer deals with some problems of terrestrial 

 magnetism, especially with the question whether the 

 sudden commencements of magnetic storms are simul- 

 taneous in occurrence at different places. The views which 

 he expresses on^ this subject are similar to those already 

 given by him in Nature. Dr. Bauer also refers to a 

 different type of storm having effects appreciable over only 

 limited areas, but does not say explicitly whether the type 

 is essentially different from the " polar elementary " 

 storms described by Prof. Birkeland in the .Arctic or the 

 " special type of disturbance" recorded in 1002-3 in the 

 .Antarctic. Towards the end of his address, Dr. Bauer 

 states that modern researches point to the conclusion that 

 attempts to represent the earth's magnetic field by a 

 Gaussian potential are of doubtful value, owing to the 

 enormous number of Gaussian constants required to repre- 

 sent anything beyond the more general features. 



The annual report of the council of the Institution of 

 Mechanical Engineers for the year 19 10, which was adopted 

 at the general meeting on February 17, deals with the chief 

 directions of the progress and work of the institution. The 

 work of the alloys research committee has been continued 

 at the National Physical Laboratory, and it is expected 

 that the tenth report will be presented for discussion during 

 the current session. It will deal with the binary system of 

 alloys of aluminium-zinc, together with some preliminary 

 results obtained in a ternary system of aluminium-zinc- 

 copper, the quantity of copper being limited in amount. 

 The work of the gas-engine research ccwnmittee has been 

 continued at the University of Birmingham, and Prof. 

 F. W. Burstall is preparing a report dealing with a new 

 series of tests on the experimental engine at the University, 

 varying only the ratio of air to gas, dealing also with the 

 composition of the charge during expansion. Prof. 

 H. C. H. Carpenter has concluded his research, referred 

 to in the 1907 report, upon the production of castings to 

 withstand high pressures. Of the remaining researches in 

 the hands of special committees, that on the value of the 

 steam-jacket is in abeyance at present, while that on the 

 friction of various gears is awaiting the publication of the 

 results of some experiments in the United States. It has 

 been decided not to undertake experiments on " heat trans- 

 mission " at present. 



In the No'.ember (1910) number of the Bulletin of the 

 Bureau of Standards Mr. B. McCollum describes and 

 investigates the theory of a new form of dynamometer for 

 the measurement of the quantity of electricity which flows 

 through the instrument. It consists of a relatively large 

 fixed coil with its axis horizontal, at the centre of which 

 is suspended, by a long vertical wire, a smaller coil with 

 its axis parallel to that of the larger coil. .Attached to 

 the moving coil is a cylinder of some homc^eneous material 

 with its axis coincident with that of the suspension. When 

 the current is sent round the coils, a magnetic couple acts 

 NO. 2156, VOL. 85] 



on the moving coil, tending to hold it with its axis parallel 

 to that of the fixed coil, and if the moving coil is dis-* 

 placed it will oscillate about its axis of suspension. The 

 quantity of electricity which passes through the c<m1s 

 during n swings of the coil is equal to 



2»n v'K(i-T»/T,*)/C, 

 where K is the moment of inertia of the moving system, T 

 the time of swing with, T, the time without the current, 

 and C i; the constant of the coils which can be calculatetl 

 from their dimensions. The investigations of the author 

 appear to promise a degree of accuracy in the measure- 

 ments comparable with that of the current balance. 



The Central of January contains an article on " Crystal 

 Structure and Chemical Composition " from the pen of 

 Prof. W. J. Pope, F.R.S. It is no exaggeration to s.'iy 

 that the theory which has been so admirably developed in 

 recent years by Mr. Barlow and Prof. Pope is likely to 

 prove equal in value with the work of Pasteur, van 't Hoff, 

 and Le Bel, which culminated in the enunciation of the 

 theory of the tetrahedral arrangement of the valencies of 

 the carbon atom. The systems of close-packed spheres 

 devised by Messrs. Barlow and Pope certainly give a more 

 realistic picture of the actual arrangement of the atoms in 

 the molecules of a crjstal than the wide-spreading models 

 which are commonly used to represent the tetrahedral 

 theorj-, although the latter are of greater service in inter- 

 preting the chemical changes which the molecules may 

 undergo. The widespread appreciation of the new theories 

 of crystal structure has been hindered by the scanty dis- 

 tribution of crystallc^raphic knowledge and by the 

 difficulty of visualising the diagrams by which its essential 

 features are expressed ; a popular and simple exposition of 

 his views by one of the authors of the theory is therefore 

 doubly welcome. The same issue contains articles by 

 Prof. Dalby on " The New Engineering Laboratories of 

 the Central Technical College," by Mr. Tripp on " Cross- 

 Channel Steamers," by Mr. Branch on " The Bonus 

 System in a Machine Shop," and by Mr. Montgomery on 

 '* The Devel<^ment of the Humphrey Pump." 



The Silica Syndicate, Ltd., 82 Hatton Garden, London, 

 E.C., has issued an illustrated descriptive catalogue of its 

 transparent quartz-glass apparatus. Transparent quartz 

 glass does not crack on subjection to violent and sudden 

 changes of temperature. Its melting point is indefinite, 

 but may be taken at about 1600° C. ; there is, however, 

 no trace of fusion at 1555° C. .Above 1000° C. it is per- 

 meable to hjdrc^en. Its expansion up to 1000° C. is 

 regular ; above 1 100° C. it contracts. The catak>gue gives 

 particulars of the numerous pieces of apparatus obtainable 

 in this useful material, tt^ether with the current prices. 



Bulletin No. 43 of the University of Illinois contains 

 an account, by Prof. E. C. Schmidt, of experiments oa 

 freight-train resistance and its relation to average car 

 weight. The tests were conducted by the Railway 

 Engineering Department of the University of Illinois in 

 1908 and 1909; all were made by means of a dynamometer 

 car owned jointly by the University and the Illinois 

 Central Railroad, and were carried out on the Chicago 

 division of this road. Results of tests on thirty-two 

 ordinary freight trains are discussed ; the average weight 

 per car ranged from a minimum of 16-12 tons to a maxi- 

 mum of 6992 tons, and the number of cars in the train 

 varied from twenty-six up to eighty-nine. The results 

 may be expressed by an equation 



R = a+bS + cS', 

 in which the coefficients a, b, and c depend on the average 

 weight W of the cars in the train in tons ; S is the speed 

 in miles per hour, and R is the resistance in pounds per 



