July 16, 1920] 



SCIENCE 



61 



to these points. The effect probably would 

 be concentrated on the surfaces of maximum 

 strain and shear. 



The results of this enquiry may be of fun- 

 damental significance in theories of the origin 

 of oil. The writer will appreciate any in- 

 formation thereon. 



Chester W. Washbuene 



60 LiBEBTT STEEET, 



New Tohk Citt 



THE CAUSES AND PREVENTION OF AFTER 

 CORROSION ON THE BORES OF FIREARMS' 



The report of an experimental study, con- 

 taining also a careful review of the scientific, 

 patent, and trade literature and a compila- 

 tion of empirical experiences which have 

 variously attributed after-corrosion on oiled 

 bores as due to powder acids, diffusing gases, 

 primer acids, metal fouling, and chlorides. 



Humidity relations, chemical examination 

 of the corrosive residue, special ammunition, 

 and a study of many so-called " gun oils " and 

 " nitrosolvents " showed : 



The infantry service cartridge leaves no 

 nitrocellulose or acid residue. The after- 

 corrosion is caused by (1) the deposition of a 

 water soluble salt or salts capable of giving 

 corrosive solutions, (2) the presence of a hu- 

 midity high enough to form a liquid film, and 

 (3) the presence of oxygen. In the service 

 ammunition, the decomposition of the chlorate 

 of the primer furnishes the only water soluble 

 salt. Pits and tool wounds retain this, so that 

 it can not be removed mechanically. It may 

 be dissolved by water. Coirosion may also be 

 prevented by stoppering the bore or by alter- 

 ing the composition of the primer. A number 

 of the non-aqueous comxwsitions sometimes 

 recommended for cleaning rifles are of no 

 value. Their virtues apparently rest on tests 

 conducted at humidities so low that no 

 corrosion could occur. 



The paper is illustrated with photographs 

 and photomicrographs. It presents a simple 

 test for differentiating between worthless and 

 useful " nitrosolvents " and also discusses the 



1 Published by permission of the director of the 

 U. S. Bureau of Mines. 



corrosive effects of black powder and low 

 pressure nitrocellulose powders. 



WlLBERT J. HUFP^ 



BuEEAu or Mines, 

 Washington, D. C. 



SCIENTIFIC BOOKS 



An Introduction to Entomology. By John 

 Henry Comstock, Professor of Entomology 

 and General Invertebrate Zoology, Emeritus, 

 in Cornell University. Ithaca, N. Y., Com- 

 stock Publishing Company. 1920, xviii + 

 220 pages, 220 figs. 



The dean of American entomologists has 

 just issued the first part of a second edition, 

 entirely rewritten, of his long-known text-book 

 called " An Introduction to Entomology." It 

 covers the structure and metamorphosis of in- 

 sects, and it covers these subjects in such com- 

 plete and thoroughgoing way and, at the same 

 time, in such compact manner, as to make the 

 book by all odds the very best of extant texts 

 to put into the hands of entomological and 

 zoological students. It will be indispensable 

 for beginning students; it will be very useful 

 for advanced ones. 



Such large compendiums as Berlese's (as 

 yet only available in the original Italian), and 

 Sharp's (in the English " Cambridge Natural 

 History") and Packard's " Text -book of Ento- 

 mology," are all of a character which lim- 

 its their use in the laboratory to that of refer- 

 ence books; they are too extended and expen- 

 sive, to say nothing of their less adapted 

 organization and general make-up, to permit 

 their use as actual individual laboratory 

 handbooks. Comstock's book fills exactly the 

 long-felt need. It contains all the knowledge 

 up to the very present, carefully analyzed, 

 sifted, and a great part of it actually contrib- 

 uted or tested by Comstock and his students, 

 that the general student of insect structure 

 and xwst-embryonic development needs to 

 know. And it is all packed away, in perfect 

 arrangement, with elaborate analytical con- 

 tents, sufficient index and bibliography and 

 carefully chosen illustrations, in about two 

 2 Chemist, Pittsburgh Experiment Station, Bu- 

 reau of Mines. 



