THE VESSEL, THE APPARATUSES AND THEIR APPLICATION. 



Fig- 3- 



On the wheel were rolled up 4,000 fathoms of line, and this was — when the machine was not 

 in use — stowed away in train-oil in a tank made for this purpose. 



The lead-line was bright steel wire of o.92 mra diameter, and with a breaking strain of 

 i/O k 2; it was delivered by the firm Felten & Guillaume in Miihlheim am Rhcin, in lenghts of about 

 2,000 fathoms. 



The deep-sea thermometer. On the first voyage was used the 

 common Negrctti & Zambra thermometer placed in Managhi'% turning-apparatus. 

 A great defect with this thermometer is, that frequently it cannot be trusted 

 when it has been used for some time. — After it has been turned, the mercury 

 will sometimes during the heaving in make its way out of the reservoir. 



We had a sad experience of this on board the Ingolf on the first voyage. 

 After a few series had been taken, some of the thermometers commenced to 

 show temperatures, which undoubtedly were wrong, and they had therefore to 

 be re-measured with other instruments, and it was not long before the greater 

 part of our stock of thermometers was unfit for use, as the mercury often filled 

 up the tube of the thermometer entirely, after it had been used. This was a 

 great inconvenience, as in concequence of this, the taking of series was made 

 very troublesome, so that the observations had to be limited as much as possible. 



When the aforesaid thermometers were turned in the hand, they always 

 showed the correct temperature, and this was likewise the case with the thermo- 

 meter attached to the hemp stray-line of the lead-line. This inconvenience did 

 not manifest itself till the thermometer was attached to the thermometer-line. 

 Mr. Knudsen proved that by giving the lower end of a thermometer a light 

 push against a hard object, mercury would run down from the reservoir. It 

 must therefore be supposed, that by taking series, the running down of the 

 mercury was due to the vibrations or the jerks which the line is exposed to, 

 when at one moment the vessel is heaved over against the line, and the next 

 moment away from it. 



During the preparations for the Ingolf-Expedition, it had come to my 

 knowledge that on former expeditions, the aforesaid inconvenience had been 

 noticed to exist with the Negretti & Zambra thermometer, and I ordered there- 

 fore from the optician Mr. Chabaud in Paris three thermometers, of which it 

 was expressly declared, that they did not suffer from the aforesaid defect. 



Most unfortunately these thermometers did not come up to what had 



been promised. On reception of the thermometers in Copenhagen, one of them 



, , , , , , • , ,-, lL , Negre "' ** M. KnudsenS 



always broke off at the same place when being turned, which probably must Zambra'% therm. 



have been due to an air-bubble in the mercurial column; as to the two others, 



it was seen immediately — on their being used — that they could not be relied upon, they were just 



subject to the very defect, against which we desired to protect ourselves when we bought them. 



For the second voyage of the Ingolf, Mr. Knudsen had constructed a thermometer, which in 



The Ingolf-Expedition. I. i. * 



