September 11, 1914] 



SCIENCE 



881 



king aqueous extracts of our brown soils. The 

 phenolsulfonic acid test for nitric acid is not 

 applicable to sucb soils due to the interference 

 of these pigment reactions. We were not satis- 

 fied with the results obtained in the experi- 

 ments already given so we repeated them on a 

 stm larger scale, but with the same results 

 which we consider as positively establishing 

 the fact that the azotobacter do not nitrify but 

 that the pigments which they form may give 

 with phenolsulfonic acid, especially in very 

 dilute solutions, a color reaction deceptively 

 similar to that given by nitric acid and this 

 reagent. Wm. P. Headden 



CoLOKABo Experiment Station, 

 Ft. Collins, Colo. 



northern lights in summer 

 I live at Nett Lake, Minnesota, 140 miles 

 northwest of Duluth and 38 miles south of 

 Fort Frances, Ontario, Canada. On the night 

 of July 4 there was a fine display of northern 

 lights (aurora borealis). It was as fine a dis- 

 play as is seen in this section even in the 

 coldest months. There were spires and rolls 

 of light and a bow of light which covered 

 the whole northern sky and towards midnight 

 reached nearly to the zenith. 



Albert B. Eeagan 

 Nett Lake, Minn., 

 July 6, 1914 



SCIENTIFIC BOOKS 

 The Cambridge Manuals of Science and Litera- 

 ture. Edited by P. Giles and A. 0. Sewakd. 

 New York, G. P. Putnam's Sons. 

 A review of the Cambridge Manuals ap- 

 peared in Science of April 18, 1913 ; but since 

 that date numerous additional volumes have 

 come to hand, dealing with the most diverse 

 topics. I give a list, with a few comments. 

 The Flea. By Harold Eussell. 



When, some years ago, a member of the 

 wealthy house of Rothschild took to collecting 

 and describing fleas, there was a tendency to 

 regard the circumstance in a humorous light, 

 and perhaps even to enquire whether a man, 

 to whom so many doors of opportunity were 

 open, could not find something better to do. 



To-day, the connection between fleas and the 

 plague having been established, Eothschild 

 finds himself the greatest living authority on 

 a subject of the highest importance to medical 

 men, and no well-informed person has any- 

 thing but praise for his work. The oriental 

 rat-flea, the one mainly concerned in the spread 

 of bubonic plague, was first made known to 

 science by Eothschild, and the development 

 of psyllology is illustrated by the collection 

 of about a hundred thousand specimens at 

 Tring. 



Mr, Eussell has had the advice of Mr. 

 Charles Eothschild, and we may assume that 

 his readable little book is up-to-date. It 

 should be in the hands of medical men and 

 the public generally, especially in regions 

 where fleas are abundant. We would venture 

 to suggest that if another edition appears the 

 exceedingly crude text-figures should be re- 

 placed by better ones ; that on page 81, in par- 

 ticular, is really scandalous. 



Bees and Wasps. By 0. H. Latter. 



This also is illustrated by very rough figures, 

 without much pretence to accuracy in detail. 

 The point of view is strictly British, but as 

 many genera are common to Europe and 

 America, the descriptions are more or less 

 applicable to our species. The excellent ac- 

 counts of the habits of English bees and wasps 

 could scarcely at present be duplicated in this 

 country, owing to the lack of observations. 

 The work of the Peckhams on the solitary 

 wasps, and that of various American observers 

 on particular species of bees and wasps, is 

 quite as good as anything done in Europe; 

 but we still remain largely or wholly ignorant 

 concerning the habits of many of our genera. 



The Life Story of Insects. By G. H. Cab- 



PENTER. 



This book is well illustrated, and the author 

 has not hesitated to borrow many of his figures 

 from American sources. The treatment of the 

 subject is broad, and although the work has 

 only 134 pages. Professor Carpenter manages 

 to convey a great deal of information in an 

 interesting way. This is, I , think, the best 

 brief introduction to entomology yet published. 



