abstracts: metallography 161 



studied is introduced into the balance case and its pressure is changed 

 until the beam balances. The density is computed from the initial and 

 the final pressures. The balance is standardized by similar observa- 

 tions made with the case filled with air. J. D. H. 



CHEMISTRY. — Experiments in the destruction of fly larvae in horse 

 manure. F. C. Cook, R. H. Hutchison, and F. M. Scales. 

 U. S. Department of Agriculture Bulletins 118 and 245. 1914 and 

 1915. 



Experiments during 1915 in the destruction of fly larvae in horse 

 manure. F. C. Cook and R. H. Hutchison. U. S. Department 

 of Agriculture Bulletin 408. 1916. 

 These three bulletins cover experiments extending over three j r ears 

 searching for satisfactory lar/icides for fly larvae to be applied to 

 fresh horse manure (the principal breeding place of the house fly) 

 which would be without extremely toxic properties and without in- 

 jurious action on the fertilizing value of the manure. The study 

 involved entomological, bacteriological, and chemical investigations. 



Over 50 substances have been tested of which three have been found 

 effective and practicable. Some were excluded because of their ex- 

 treme toxicity, such as potassium cyanide. The three that are recom- 

 mended are borax, hellebore, and calcium cyanamid mixtures with 

 acid phosphate. 



Borax in large amounts injures plant growth, hence should be ap- 

 plied only to manure that is not to be used as a fertilizer. 



Powdered hellebore {Veratrum album and V. viride) applied as a 

 solution is an effective larvicide and, because it is decomposed in 

 the course of the fermentation, does not affect the fertilizing value of 

 the manure even when excessive quantities are used. 



Calcium cyanamid mixed with acid phosphate and kainit are ef- 

 fective and, if enough acid phosphate has been added to give an acid 

 reaction, the nitrogen and ammonia of the manure will be retained. 

 The mixture is an advantage in that it adds to the manure nitrogen, 

 potash, and phosphoric acid. F. C. C. 



METALLOGRAPHY. — The structure of the coating on tinned sheet 

 copper in relation to a curious case of corrosion of this material. 

 Paul D. Merica. Bureau of Standards Technologic Paper No. 

 90. Pp. 18. 1917. 

 The attention of the author has been directed to a case of local cor- 

 rosion, or pitting, in tinned sheet copper roofing. The pits occur in 



