38 American Fisheries Society. 



served to point the way to further work, and to indicate the na- 

 ture of the difficulties to be encountered. Accordingly, plans 

 were made to carry out several large series of experiments, in- 

 volving the preparation, exposure in the water and testing of 

 several hundred individual samples treated by all the ordinary 

 proprietary and non-proprietary preservatives available. Since 

 the tests were repeated in many cases fifty or one hundred times 

 in order to get a fair average of results, many thousands of tests 

 were made. The samples were made in sets of seven by each 

 method, one to be held as a check, and the six to be taken up 

 from the water at intervals of three weeks to two months, the 

 test usually running six months. Most of the exposures hitherto 

 made in the European experiments have lasted less than two 

 months. By way of describing these experiments, the results 

 will be presented in connection with the different factors con- 

 cerned and the methods of measuring them. 



The work was limited to (1) those non-proprietary preserva- 

 tives that are in widespread use or have been known by in- 

 vestigation to be superior as net preservatives ; (2) copper oleate 

 as a promising prospect for a new preservative ; and (3) all pro- 

 prietary net preservatives on the market or in preparation for 

 exploitation. These latter were obtained by means of circular 

 letters sent through the various fishery trade journals. 



1. Control. 

 A, White line, no treatment. 



2. Non-proprietary Preservatives. 

 Tar. 



F. Coal tar, distilled. Black, thick, syrupy tar. Applied cold, diluted with 



an equal volume of benzol. The benzol evaporates from the lines. 



G. Pine tar. The commercial article, consistency of thick syrup. Brownish 

 black. Applied cold, diluted with an equal volume of benzol. The ben- 

 zol evaporates from the lines. 



H. Coal tar 1 volume, pine 1 volume, benzol 2 volumes. Applied to the 

 lines cold. When the benzol has evaporated, equal parts of the two tars 

 remain on the lines. 



Tanning Methods: 

 I. Bull's method. A 20 per cent solution of solid extract of quercitron 

 in water is prepared, and heated nearly to boiling. The line is steeped 

 in the hot dtcoction until the latter is cold, then taken out and dried. 

 The line is given the same steeping a second time, dried, and finally 

 mordanted with a 3 per cent solution of potassium bichromate. (For 



