HYDROGRAPHIOAL SURVEY. 191 



iiithoms, and felt assured that, if it had stnick the 

 bottom, I should have observed it ; for the whole 

 of the line in use, was not above twice as heavy as 

 the lead ; so that the diminution of one-third of the 

 weight, would have been very observable. But, 

 with a heavy lead and thick line, where the strength 

 of several men is requisite to haul it up, there can 

 be no evidence, without the test of weighing, of any 

 trifling alteration in the strain or weight. Hence, 

 if the lead is found to have been at the bottom, 

 there can be no assurance that a quantity of the 

 line, as well as the lead, has not also been on the 

 ground. To a 20 lb. or 28 lb. lead, I generally attach 

 200 or 300 fathoms of common log-line, where there 

 is no valuable apparatus along with it, and to this a 

 small lead-line, and finish with a deep-sea line, thus 

 increasing the line in thickness, with the increase of 

 weight to be supported ; and having the whole of 

 such a weight that the line can be held in the hand, 

 and the least stoppage made perceptible. 



At great depths, the effect of the pressure of the 

 sea is not a little curious. My Father met with 

 the following singular instance, in the year 1794, 

 which I have taken from his log-book. 



On the 31st of May, the chief mate of the Hen- 

 rietta of Whitby, the ship my Father then com- 

 manded, struck a whale, which " ran" all the lines 

 out of the boat, before assistance arrived, and then 

 dragged the boat under water, the men mean while 



