RECORDS OF MEETINGS 207 



certain bacteria on certain substances and the mere number of bacteria, 

 without distinction as to kinds, bears no relation to it. The best cri- 

 terion for decomposition would be a chemical test for decomposition 

 products, but no such test has yet been shown to be of general value. 



Dr. Hussakof gave an account of a trip he had recently made to Mis- 

 sissippi for the purpose of collecting specimens of the paddlefish, 

 Polyodon spathula, for the preparation of an exhibition group in the 

 American Museum. This fish is one of the largest and most interesting 

 found in our fresh waters. It is especially abundant in the lower Mis- 

 sissippi Valley, where it attains a length of 6 feet and a weight of 160 

 pounds. Some interesting facts were presented, bearing on its natural 

 history and its commercial value. Polyodon roe is said to produce the 

 best caviar in the world. The distribution of Polyodon and of the re- 

 lated Chinese fish, Psephurus, was discussed. 



The paper was illustrated with lantern slides. 



The Section then adjourned. L. Hussakof, 



Secretary. 



SECTION OF ASTRONOMY, PHYSICS AND CHEMISTRY. 



15 May, 1911. 



Section met at 8:15 p. m., Vice-President Campbell presiding. 



The minutes of the last meeting of the Section were read and approved. 



The following programme was then offered : 



William Campbell, Notes on Antifriction Metals. 



Summary of Paper. 



■ Starting with a series of Thormal diagrams for binary alloys. Or. 

 Campbell developed certain ternary diagrams and explained many n\' the 

 common bearing metals thereby. Then, by means of lantern slides, the 

 following systems were discussed and their structures shown : 



1. Lead antimony tin. 



2. Tin antimony copper. 



3. Lead tin antimony copper. 



4. Zinc-rich alloys such as lumen, etc. 



5. Tin-zinc-rich alloys : Parson's white brass, etc. 



Then by way of contrast, numerous alloys rich in copper, with and 

 without lead, which are used for bearing, were shown and their structures 

 and properties explained. 



The Section then adjourned. Edward J. Thatcher, 



Secretary. 



