PRESERVATION OF EISH NETS. 15 



bichromate with the cutch destroys any preservino: power the cutch 

 alone may have. The small differences between the different varieties 

 of cutch' and the dill'orcnt modes of h;ui(llin<r. cxchisive of the 

 bichromate after treatment, are not sijrnificant. 



The following is another series of experiments made by Cunning- 

 ham in which quebracho and cube gambler were tried : 



The pieces in this case were left in tlie harbor from May 28 to July 15, a 

 period of seven weelvs. The pieces of net were cnt from another new net, whicti 

 seems to have i)(>en of better quality than that previously used, as the pieces 

 cured with cutch alone were not so weak after exposure as in previous experi- 

 ments ; 



rounds. Ouncps. 



I. Mangrove B, alone, 1 pound to 1 gallon water, dipped once, 



soaked 10 minutes 12 5 



12. Quobracho alone, same strength, same treatment 9 •") 



3. Cube gambler alone, same strength, same treatment 5 



4. Mangrove B, as before, then dipped in hot bichromate, 1 ounce 



to 1 gallon water 13 8 



5. Quebracho as before, followed by bichromate, 1 ounce to 1 8 



gallon VI 14 



G. Gambler as before, followed by bicromate, 1 ounce to 1 gallon __ 11 5 



7. Mangrove B, 1 pound, soda 1 ounce to 1 gallon water, net dipped 



in mixture then dipped in bichromate, 1 ounce to 1 gallon 



water 7 8 



8. Gambier with soda, then bichromate in above proportions 7 12 



9. Mangrove B, one-half pound to one-half gallon water, mixed 



with one-half pint bichromate solution, 1 ounce to 1 gallon 7 8 



10. Quebracho mixed with bichromate, same proportions 10 10 



II. Quebracho, one-half pound, bichromate one-half ounce to 1 



gallon water, together .") 10 



Again, it is shown that bichromate, if used as a separate after- 

 treatment, greatly increases the preserving effect of the tanning mate- 

 rials; it also further confirms the conclusion that bichromate mixed 

 with the tanning material does harm rather than good. Soda added 

 to the tanning extract previous to use is rather harmful than other- 

 wise, as shown by trials Nos. 7 and 8. 



LINOEMAN'S EXPERIMENTS. 



Thv. Lindeman (1.S97), in the prize-v>dnning paper submitted in 

 competition before the Trondhjem P'ishery Society in 1896 for the 

 best paper on preservation of nets, seems to have been first to use the 

 dynamometer, or breaking-test, method of studying the preservation 

 of nets. On two kinds of thread, hemp and cotton, he tried 12 pre- 

 serving materials in comparison with untreated thread, as follows : 



T. Thread, without treatment. 



II. Bluestone. — 1* kilos (3.3 pounds) bluestone, 1 barrel water. Net lies in 

 this 1 day, washed out without drying, and then put directly into the 

 sea. 



III. Catechu with mordant.— To 7* kilos (16.2 pounds) net, take 1 to li kilos 



(2.2 to 2.7.5 pounds) catechu, which is boiled until dissolved; add 60 

 grams (2 ounces) bluestone. The net is put in this bath while it is 

 warm (60° C. or 140° F.) and allowetl to stand over night. The next 

 day it is well drained and brought into a bath (80° C. or 176° F.) in 

 which is dissolved LSO grams (6.4 ounces) potassium bichromate. 



IV. Catechu with linseed oil. — The net is prepared according to III, dried by 



artificial drying, and brought into warmed raw linseed oil, in which it 

 lies until next day ; it is then taken out, freed as much as ixjssible 

 from the oil, and dried in air. 



