62 U. S, BUREAU OF FISHERIES. 



all the water is driven off, during which time the temperature does 

 not rise far above 212° F. (100° C). When bubbles of steam cease 

 to escape, the temperatiu-e will rise slowly until 45 pounds' pressure 

 of steam is maintained in the jacket, the copper oleate comes to a 

 temperature of 257 to 268° F. (126 to 132° C.), and the mass is a 

 thick green liquid. When this temperature is reached, an air hose 

 nozzle is so placed that air is blown in and bubbles through the hot 

 mass from the bottom. Stirring now helps to incorporate the air 

 bubbles in the mass and to accelerate oxidation. As the mass absorbs 

 oxygen, it becomes very viscid, so that a stick inserted- in it and 

 brought out carries a sticky bulk which in large part hangs without 

 dropping. The blowing requires about one-half hour. The blowing 

 of air is, of course, for the purpose of oxidizing the mass with as 

 much oxygen as it will spontaneously absorb at this elevated tem- 

 perature, so as to diminish the likehhood of spontaneous heating of 

 fish nets to which it is applied. 



When the consistency just described is reached, the batch is con- 

 sidered finished, a lot sample is taken, and to the batch is added the 

 amount of oil necessary to prevent creeping. If oil is used, it should 

 be mineral lubricating oil in the proportion of 3 pints for the 

 batch as described. Later experiments, however, indicate that creo- 

 sote answers the same purpose more cheaply and more effectively. 

 Creosote is a good preservative itself; it prevents the copper oleate 

 from creeping to the surface of lines and can be bought for 50 cents 

 per gallon or less. If creosote is used, 1^ to 2 pints to the batch 

 quantity described is sufficient. The creosote used in the work 

 herein described has the following properties: A thin mobile brown- 

 ish but rather transparent liquid; specific gravity, 980; smell, smoky. 

 It is the grade used for preserving wood. 



When the oil or creosote has been added and thorouglily mixed 

 into the mass, the latter is poured into cans or other containers and 

 set aside to cool. A record is kept of each batch, wliich is designated 

 by number. If cans are used, they may be of tlie friction-top type. 

 The contents of a 5-pound can will;^ when dissolved in 5 gallons of 

 gasoline, treat between 50 and 60 pounds of cotton net. Wlien dis- 

 solved in 2h gallons of gasoline, it will treat 25 to 30 pounds of net 

 with a comparatively heavy deposit of the preservative, suitable for 

 severe conditions. For combining tar the contents of a 5-pound can 

 are dissolved in 5 gallons of benzol and 5 gallons of coal tar are added 

 and mixed, making about 10;^ gallons of a preservative, suitable for 

 traps and other gear, subject to the severest exposure. The nets are 

 dipped in the mixture cold and are hung out to dry. Drying takes 

 about 24 hours. It may also be applied separately to the lines, as 

 will be described below, the lines then to be tarred in the usual way. 



METHOD OF APPLYING COPPER OLEATE TO NETS. 



The copper oleate as canned is dissolved in gasoline. If it does not 

 already contain the oil or creosote, one of these must be added in 

 the quantity indicated. The cold, waxy, copper oleate dissolves 

 rather slowly in gasoline, but the can may be put in boiling water 

 for a few minutes, until the copper oleate is liquefied; it then dissolves 

 quickly. The gasoline solution should bo contained in a metal vessel 

 (a galvanized-iron washtub, for example) ; the net is dipped into this 



