28 U. S. BUREAU OF FISHERIES. 



these figures are 14.6, 13.2, and 6.4 kilograms, respectively. Then, 

 to show the practical force of his argument, he points out that with 

 the untreated net (No. 1) with stone sinkers one must work with 

 the weight of the net, 8.6 kilograms plus the water soaked up, 19.5 

 kilograms plus the stone sinkers, 24 kilograms, or 52,1 kilograms 

 all together. While with the barked and tarred net and lead sink- 

 ers these weights are, net, tanning material and tar, 15.7 kilograms ; 

 absorbed water, 8.5 plus the necessary lead, 0.4 kilogram; a total 

 of 30.6 kilograms. He also shows that the first net, requiring 17 

 men to handle it, can, if its weight is reduced by barking and 

 tarring, be handled by only 10 men. No argument is required to 

 show, also, that of two nets made of material exactly the same 

 size and quality, but one weighted down to nearly twice the weight 

 of the other, the heavier will wear faster than the lighter. While 

 space does not permit of an extended review of the discussion of 

 these matters,** it should be pointed out that Jessen appears to 

 have overlooked the fact that if a tarred net of a weight of 3.15 

 increases in weight by 54 per cent, it will weigh 4.85 in all, while 

 the untreated net of 1.45 will, when increased by 227 per cent, weigh 

 4.95, or more than the tarred one. Bull, in the article referred to 

 in the footnote, gives the correct mathematics for making the cal- 

 culations. 



Cunningham's further experiments. 



At this point it is ajJpropriate to introduce the remaining experi- 

 ments conducted by Cunningham, using all the ordinary net preserv- 

 atives in various ways. 



PREPARATION OF SAMPI.ES. 



1. Ciiteh alone (one-half pound cutch boiled in one-half gallon of water). — 

 The pieces of net put in this luitil well soaked, then dried. Then put into cutch 

 of same strength, steeped for two days, then dried. 



2. Cutch and glue (one-half pound glue dissolved in 1 gallon of water). — The 

 net dipped into this, then squeezed and put into hot cutch — one-half pound cutch 

 to one-half gallon of water — then dried. Afterwards dipped a second time Into 

 cutch of same strength and dried again. 



3. Cutch, glue, and bichromate of potash. — The net was dipped into glue, 

 1 pound to one-half gallon of water, with a little bichromate of potash added ; 

 then put into cold cutch and left to steep two days. 



4. Cutch and copper sulphate. — The net was steeped two days in cutch, one- 

 half pound to one-half gallon of water, then, while wet, put into copper sul- 

 phate, 1 pound to one-half gallon of water, and after a short soak rinsed in 

 fresh water and dried. 



.5. Cutch and coal tar. — The net was first saturated with coal tar, then squeezed 

 and wrung out several times with hot water, then dried for a week, and after- 

 wards dipped in hot cutch, one-half pound to one-half gallon of water. 



6. Cutch and coal tar mixed. — One-half pound cutch boiled in one-half gallon 

 of water and then about a pint of coal tar stirred into the hot solution. The 

 net was dipped into the hot mixture, then dried. 



7. Cutch, tar, and green oil |a creosote distilled from coal tar]. — The net was 

 first steeped three days in cutch, one-half pound to one-half gallon of water. 

 Then the same ciitch was heated and the net passed hot from this through a mix- 

 ture of coa! tar. Stockholm [piuel tar, and green oil as thick as paint. The net 

 was then passed through a wringing machine and dried. 



" See further. Bull (1000). Roference Is made by Bull to a discussion of the matter 

 between Dr. Johan Hjort and Peter Jessen In the Bergens Tidende, presumably in 1906. 



