256 



NATURE 



[November 4, 19 15 



as a practical method of identification or as an 

 intellectual exercise is open to question; we are 

 inclined to think that it is neither the one nor the 

 other, and that the table should only be consulted 

 when the group character of the compound has 

 been definitely ascertained. 



The fact that the book is written by a native 

 of Bengal and printed by a Calcutta firm explains 

 the occasional lapses in English, which is by no 

 means to the discredit of either publisher or 

 author ; but it does not excuse the far too numerous 

 mistakes in the spelling of chemical names. It is 

 unfortunate that the volume has not been read in 

 proof by someone conversant with the language. 



J. B. C. 



OUR BOOKSHELF. 

 The Callendar Steam Tables. By Prof. H. L. 



Callendar. Pp. 39. (London : Edward Arnold, 



1915.) Price 35. net. 

 In his Royal Society paper in 1900 and in his 

 article on Vaporisation in the " Encyclopaedia 

 Britannica " of 1902, Prof. Callendar showed the 

 use of a simple empirical formula connecting the 

 pressure, density, and temperature of steam. If 

 his formula is correct, it is possible to tabulate 

 all the properties of steam required in engineering 

 calculations in such ways that the numbers are 

 more consistent with one another than any hitherto 

 published. MoUier, of Dresden, published tables 

 and corresponding curves calculated by this 

 method, and these were republished in England 

 by Ewing in 1910. Messrs. Smith and Warren 

 calculated and published tables which were dis- 

 cussed in Nature of April 3, 1913. We then gave 

 reasons for the suggestion that perhaps such ex- 

 perimental results as were available scarcely justi- 

 fied the use of the Callendar method, in spite of 

 the fact that Prof. Callendar is undoubtedly the 

 highest authority on this subject. He now says 

 that these tables form part of a larger work en- 

 titled "Properties of Steam," in which the theory 

 of steam and experimental methods of investiga- 

 tion are more fully discussed and illustrated. 



For the present we may, perhaps, assume that, 

 for moderate pressures and temperatures, these 

 tables are more correct than any hitherto pub- 

 lished, and if this is so their value to the steam 

 engineer cannot be over-praised. They give 

 pound Centigrade and also pound • Fahrenheit 

 units, with pressures in pounds per square inch, 

 volumes in cubic feet per pound, as well as kilo- 

 gram Centigrade units, with pressures in kilos 

 per square cm. and volumes in cubic metres 

 per kilo. Table II. is the most important; it gives 

 volume, entropy, temperature, and total heat in 

 terms of pressure. Tables IV., V., VI., and VII. 

 give the total heat, volume, entropy, and Gibbs's 

 potential of super-heated and super-saturated 

 steam. The diagram which accompanies the 

 tables has been arranged for interesting graphi- 

 cal calculation. From, this description steam 

 NO. 24.01, VOL. 96] 



engineers will see that, in addition to what is due 

 i for his engine experiments in Montreal, they owe 

 the author a second deep debt of gratitude. The 

 gas and petrol engine engineers also owe him a 

 large debt. We do not think that there is any case 

 of an experimental physicist since Regnault's 

 time doing even half as much service to engin- 

 eering. J. P. 



The Star Pocket-hook, or How to Find your Way 

 at Night by the Stars. By R. Weatherhead. 

 Second impression. Pp. 92. (London : Long- 

 mans, Green and Co., 1915.) Price i5. net. 

 This little manual not only provides an easy 

 means of becoming familiar with the chief con- 

 stellations and individual stars, but also shows 

 how this knowledge may be made practically 

 useful in the determination of position and direc- 

 tion during night marches. The book contains 

 several useful tables giving among other details 

 the time of year when certain stars transit at 

 midnight, the highest altitudes of stars in various 

 latitudes, and pairs of bright stars which transit 

 at the same time. These simul-transit pairs, when 

 vertical, mark the meridian, and also serve as 

 pointers to a celestial pole. The new issue of the 

 book includes some additional notes on the use 

 of the stars as direction and time finders ; and it 

 should be found particularly helpful to soldiers 

 and scouts at the present time. 



The Cambridge Pocket Diary, 1915-1916. Pp. 



XV -1-255. (Cambridge: At the University 



Press, 1915.) Price is. net. 

 Readers whose work is connected with schools 

 and colleges will find the arrangement of this 

 attractively produced pocket diary very con- 

 venient. Beginning in the middle of September, 

 it enables one to start a new diary at the com- 

 mencement of the academic year. The miscel- 

 laneous information provided is intended primarily 

 for members of the University of Cambridge. 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous communications.] 



The Manganese Ore Requirements of Germany. 



In a letter, under the above title, published in 

 Nature of October 14, Dr. Leigh Fermor dissents 

 from the conclusion reached in my article of July 15 

 on munition metals that the enemy countries can 

 produce sufficient manganese for their steel manu- 

 facture requirements without having recourse to im- 

 ports, and gives it as his opinion that they are likely 

 to be seriously hampered by a shortage of manganese 

 ore as soon as their accumulated stocks have been 

 used. His conclusions are as follows : — 



" (a) That on the outbreak of war the Teutonic 

 Powers had no great accumulated stocks of manganese 

 ore, perhaps a maximum of 200,000 tons ; (b) that, 

 assuming war conditions necessitate a maintenance of 

 the iron and steel industries of those two countries at 



