334 



THE FUR SEALS OF THE PRIBILOF ISLANDS. 



The hand rheostat to which the cautery wire was attached had, in its final form, 

 simply a coil of iron wire short circuited by a heavy lever arm and plug "cut out" 

 inserted in series with the wire. 



The connections , were as represented in the figure: a, j)lug cut out; />, cautery 

 wire; c, iron wire resistance; d, lever arm; c and /, terminals to be connected to the 

 dynamo. 



After the dynamo of low voltage was completed, a run of five hours was made 

 with the current at its full value, to test the plant. The test also showed that the 

 current could be controlled by the rheostat, and was large enough to keep the cautery 

 wire white hot during the burning. 



Our practical work with the apparatus shows that improvement can be made on 

 the present handle, in tlie method of holding the cautery wire, and also in the form 

 of the lever for the control of the current. Tlie least weight possible was put into the 

 plant, as it was supposed to be necessary to carry it by hand from place to place. 

 This made parts of the apparatus too light. For ])ermanent work a heavier plant 



^\wumi& 



mounted on wheels would be better suited to the conditions. Tliere are few of the 

 rookeries which <!an not be reached with a team. 



THE FIRST TKSTS. 



The first tests were made on dead pup skins soon after the apparatus reached the 

 island, and were a failure. The engine furnished an insufficient amount of power to 

 burn with any degree of ease through the seal fur-, which is several times denser and 

 much finer than that of the cat. 



The power generated in the earliest testa was less than that previously obtained 

 in the trial run. This was due to the following causes: A bent shaft on the engine, 

 caused by rough handling in transi)ort; slijjping of the belt; dampness in the coils of 

 the dynamo, allowing a leakage of the magnetizing current; and an inferior quality 

 of gasoline which had been supplied. 



Before the time arrived for work in active branding, these faults were corrected 

 and an improvement made in the commutation of the current, but there was still 

 insufficient power to do the branding rapidly. Two hand gears were then mounted 

 on the base between the engine and dynamo. They were belted to the vacant Hy 

 wheel and a wooden pulley mounted on the same shaft. With this arrangement more 

 power was generated than could be used. 



