REVIEWS 339 



equal and perhaps more pressing need. As civilising man spreads over the 

 world, he carries with him not only extermination but inextricable confusion 

 among the plant and animal associations whose dominions he invades, so that 

 it becomes increasingly difficult to disentangle the threads of the history of animal 

 and plant distribution. It should be the aim of systematic zoologists and botanists 

 to endeavour to reconstruct this history before it is too late, and as a valuable 

 contribution toward this endeavour the reports issued by Prof. Chilton and his 

 co-workers should be widely welcomed. GEOFFREY SMITH. 



Spark Spectra of the Metals. By Charles E. Gissing, F.R.G.S. [Pp. 21.] 

 (London : Bailliere, Tindall & Cox, 1910. Price 7^. 6d. net.) 



To spectroscopists it is a constant source of wonder that metallurgical and mining 

 analysts do not avail themselves more freely of spectroscopic methods. With a 

 standard spectrograph once installed — not a costly or a difficult matter — the 

 preliminary examination of, say, an ore becomes a matter of minutes in place of 

 hours and the results are certainly no less sure or comprehensive. Even in some 

 of our large Government laboratories the spectrograph is not recognised as an 

 essential to speedy and searching preliminary examination. 



Whilst welcoming Admiral Gissing's atlas for the reason that it may do 

 something to disturb this apathy, we feel that it can only be recognised, in its 

 present form, as a pioneer. 



For general use we consider that " arc," rather than " spark," spectra would be 

 more convenient ; space will not permit us to argue this matter here. 



Taking the author's spark spectra we find much to criticise. The wave-lengths 

 given are often not sufficiently accurate, in some cases they differ from accepted 

 standards by several tenth-metres and not infrequently, especially in the case of 

 " blends," the difference of a fraction of an A.U. draws the distinction between one 

 element and another. 



Then the complete omission of some elements is serious. In alloys and ores 

 titanium, for example, often plays a not insignificant role and gives, in the 

 spectrum, strong groups of lines to the confusion of others : yet titanium is not 

 included. On the other hand we fail to see what useful purpose can be served by 

 the introduction of the spectra of alloys ; for example, one rarely requires to test a 

 sovereign by spectroscopic methods. Besides, such an alloy as " brass wire " may 

 vary so considerably in composition that the spectrum of one sample is quite 

 useless, as well as redundant. 



The descriptions of methods, of the characteristic features of each spectrum 

 and the tabulation of the chief lines will be found useful in the practical 

 employment of the fifty photographs of spectra reproduced on the ten folding 

 plates. But here again there are omissions : surely the " triplets " of the iron 

 spectrum are characteristic enough to warrant mention in the notes. 



Finally we must protest against the arrangement of the spectra with the less 

 refrangible radiations to the left. Red to the right is the British convention, now 

 almost universally adopted, and any other arrangement must lead to confusion. 



With these criticisms we welcome the volume as a pioneer, although there are 

 of course the fine atlases of Hag'enbach and Konen — translated by Dr. King — 

 Eder &: Valenta, Kayser & Runge, etc Yet the volume under notice is a more 

 direct appeal to our impractical practicians, and if it causes them to consider 

 the spectrographic method enhanced efficiency will accrue. 



William E. Rolston. 



