638 SCIENCE PROGRESS 



the fact that the duration of the gas blow-holes is predicted by geologists 

 to be very short. The consensus of opinion is that it will be exhausted 

 in 10-15 years, and the costly plant installed will be useless. So far, no 

 army or naval airship has been filled with helium, which would seem to prove 

 that production is still very limited. 



Considerable doubt has been expressed by many people as to the wisdom 

 of the Government in crowding the universities and technical schools with 

 ex-service men ; or perhaps it would be better to say, as to the wisdom of 

 the ex-service men who have accepted government grants for this purpose, 

 since it is notorious that authorities who provide scholarships never worry 

 themselves in the least as to the ultimate fate of their victims. That these 

 doubts are likely to be justified is proved by the following extract from the 

 fourth number of the Archives oj the Cambridge University Forestry Association 

 (October 1920) : "With the exception of Indian and Colonial conservators, 

 we have heard of no appointments either by the Forestry Commission or by 

 private owners of estates. It is certain that far too many disabled ofl&cers 

 were encouraged to take up Forestry, and that there is now a large number 

 of qualified men at liberty who cannot hope to be absorbed for several years. 

 The responsibility for the flooding of the market with trained foresters is 

 divided amongst several Ministries, and it is difiicult to fix the blame on one 

 more than on another ; still, the necessity of turning to some other occupations 

 after having wasted two years naturally causes those whose wounds prevent 

 them considering posts in the tropics, to feel that they have been betrayed." 



It seems very certain that the " flooding of the market with trained 

 foresters " will be insignificant compared with the flooding with trained 

 chemists (and engineers) after the degree examinations of 1921 and 1922, 

 and bitter feehngs of betrayal are likely to become widespread among the 

 many men who are working really hard in the hope of achieving a successful 

 scientific career. 



Refractometers are used very widely by industrial chemists in their 

 routine work, but the methods of spectrum analysis have hitherto been 

 employed very little for this purpose. A little monograph published by 

 Messrs. Adam Helger, Ltd. {Optical Methods in Control and Research Labora- 

 tories, pp. 30, price IS. 6d.), shows that with suitable apparatus the spectro- 

 meter and spectrophotometer provide the chemist with an additional and 

 very powerful help towards the solution of his everyday problems. The 

 constant deviation spectrometers constructed by Messrs. Hilger enable the 

 positions of the lines or absorption bands in the spectrum of a substance 

 to be determined very rapidly, both in the visible region and in the ultra- 

 violet. By combining the spectrometer with a sector photometer or a 

 Nutting photometer quantitative measurements of the absorption can be 

 made, the whole of the data required for the construction of an absorption 

 curve being obtained on a single photographic plate. The quantities of 

 certain substances which can be detected by the presence of their charac- 

 teristic bands in the ultra-violet spectrum is extraordinarily minute. Thus, 

 Hartley and Dobbie {J.C.S., 1900, 77, 318) found that as little as o'ooooi gm. 

 of pyridine in 100 c.c. of water produced a definite eSect in the ultra-violet 

 spectrum, while 0-5 mg. of strychnine can be detected and verified by its 

 ultra-violet bands. The monograph deals also with refractometers and 

 polarimeters, and supplies a very useful bibliography to the recent literature 

 relating to each instrument. 



The Cambridge University Press announces that, instead of publishing 

 a new edition of N. R. Campbell's Modern Electric Theory, it proposes to 

 issue monographs, each corresponding roughly to a chapter of the book. 

 These monographs will be edited by Dr. Campbell, but will be written by 

 difierent authors, who will not be experts in the branches of physics con- 

 cerned. This rather novel procedure has been adopted on the ground that 



