INTERESTING SCIENTIFIC WORK IN THE ARCTIC 205 



above the true horizon. It must be remembered, however, that 

 mercury freezes at about forty degrees Fahrenheit below zero, 

 and has accordingly a very limited field of usefulness in the Arc- 

 tic. For this reason and on account of its weight some other 

 form of artificial horizon is necessary. 



Other liquids besides mercury have been used, as have also 

 glass mirrors made horizontal by means of screw legs and spirit 

 levels. These last require great care in adjusting, and there is 

 always more or less error attending their use. With the above 

 instruments one can determine his position with sufficient accu- 

 racy whenever the sun, moon or any of the principal stars are 

 visible, but, having done so, it is a matter of no small difficulty 

 to ascertain what is the proper direction in which to travel to be 

 sure of always going north. 



The compass, to which we are accustomed to look for guid- 

 ance, does not, as is well known, point to the geographical pole, 

 but to a region some distance south of it, called the magnetic 

 pole. This has been located to the northwestward of Hudson 

 Bay, and at any place between that and the true pole the compass 

 needle will point toward that pole. If to one side of the mag- 

 netic pole, it will point more or less east or west, as the case 

 may be. 



In preparing for a sledge journey in the Arctic it has been 

 found advisable to have a special chest for instruments, usually 

 secured to the front of the sledges. This should contain a sex- 

 tant, an artificial horizon of a non-freezing type, one or two chro- 

 nometers and the tables of logarithms and astronomical data of 

 the sun, moon and stars, necessary in working out observations. 



It is advisable that a pocket chronometer be carried on the 

 person, in order that it may get the warmth of the body and be 

 spared the jolting of the sledge. 



Other instruments may be carried for the collection of scien- 

 tific information, but the above are all that is necessary for loca- 



