14 U. S. BUREAU OF FISHERIES. 



labor and expense by use of potassium bichromate. To quote Cun- 

 ningham : 



Accordingly I made at Newlyn a large number of experiments * * * to 

 test whether by the use of bichromate the net could be preserved more suc- 

 cessfully or more cheaply, and the results were very favorable. One of the 

 most striking of these experiments was made entirely with Burraah cutch, of 

 the Double Eagle brand. The pieces of net used were cut from the net made at 

 Bridport, 25 rows to the yard, 12-ply cotton. The strength of the net when 

 tested new and uncured, or " white," was ISi pounds * * *. Four pieces of 

 net, cured with and without bichromate, as shown below, were put down in 

 Newlyn Harbor on January 31, 1900, and taken up and tested on March 3, so 

 that they were in the water between four and five weeks. The strengths given 

 are the averages of five trials on the testing machine : 



Pounds. Ounces. 



1. Dipped once in Burmah cutch, 1 pound to 1 gallon of water_ 4 2 



2. Dipped ticice in Burmah cutch of same strength, dried after 



first dip 6 5 



3. Dipped once in Burmah cutch, same strength, with 1 ounce 



bichromate potash added to 1 gallon cutch liquor 5 3 



4. Dipped once in Burmah cutch, same strength, then dipped 



separately in hot solution of bichromate, one-half pound 



to 1 gallon water 14 5 



It will be seen that of these four pieces of net, which were placed in the 

 harbor at the same time, fastened to the same piece of rope, three were prac- 

 tically rotten, while the fourth was nearly as strong as when new, and this 

 fourth piece was the one that had been cured with bichromate of potash. 



Dipping twice in cutch alone (No. 2) seems to improve the net 

 very little. Experiment No. 3 shows that the bichromate does no 

 good if added to the cutch solution, but must be applied separately/ 

 to be effective. The reason for this, as will be seen above, is that 

 the bichromate makes the tannins insoluble, so that they do not get 

 into the fibers at all. 



The bichromate solution used above was strong. 



The following series of tests shows the results with weaker bichro- 

 mate solution, and different combinations, nets submerged January 

 31, taken up March 30, put down again May 14, finally taken up and 

 tested May 28 : 



Pounds. Ounces. 



1. Burmah cutch, 1 pound to gallon, net put in hot liquid and 



left to soak 24 hours 4 14 



2. Mangrove cutch A, a somewhat insoluble kind ; same treat- 



ment 5 12 



3. Mangrove cutch B, another brand ; same treatment 7 6 



4. Burmah cutch, same treatment ; net then dipped in hot 



bichromate, 1 ounce to 1 gallon water 13 5 



5. Mangrove cutch A, same treatment, following by hot 



bichromate, same strength 14 9 



6: Mangrove cutch B. same treatment, followed by hot 



bichromate, same strength 18 5 



7. Mangrove cutch B, 1 pound, with 1 ounce bichromate, 



boiled together in 1 gallon water, net left to soak 



24 hour.s 1 13 



8. Burmah cutch, 1 pound, with 1 ounce washing soda, boiled 



together in 1 gallon water, net left to soak 24 hours 6 12 



9. Mangrove cutch A and soda ; same treatment 4 2 



10. Burmah cutch, 1 pound to 1 gallon sea water instead of 



fresh 5 13 



11. Mangrove cutch A, in sea water; same strength 6 5 



Here, again, it is shown that no treatment appears to do much 

 good without the after treatment with bichromate. The use of 



