42 



American Fisheries Society. 



proofing material (K), another proprietary preparation, does not 

 seem to fall into either group. These groups are averaged in 

 Fig. 2 for ease in interpretation. A simple and striking conclu- 

 sion stands out, namely, that those preservatives which have a 

 "body," or a non-volatile component which covers the fibres and 

 protects them mechanically, afford good preservation against 

 weather, while those which do not have a body, but depend on 

 toxic effects are not so good. Preservatives under air conditions, 

 or weather, therefore appear to do their work mechanically or 

 chemically rather than biologically (by destroying living organ- 

 isms). Simple covering protects the lines against the weather — 

 any preservative that covers, answers the purpose as far as 

 tensile strength is concerned. 



Table II. — Tensile strength in pounds of No. 24 cotton lines exposed 



ON the roof of the Fishery Products Laboratory, Washington, D. C., 



November 25, 1921, to May 25, 1922. 



|0ne sample of each taken up each month. Each figure represents the result of 15 breaks, except 

 that of the control (A), unexposed, which is the average of 60 tests.] 



Experiments at Key West, Florida. The lines exposed in 



