206 INTERESTING SCIENTIFIC WORK IN THE ARCTIC 



ting one's position. They should be made as light as possible 

 and secured in a watertight box, so that, although the sledge 

 may be completely upset or immersed in water, no damage can 

 come to the instruments. 



A chart of some sort is desirable, but, as in polar journeys it 

 covers a field entirely unsurveyed, it may be composed of a blank 

 sheet of paper, with a dot in the centre representing the pole. 



The drawbacks to determining one's position in the Arctic do 

 not lie in the computations, but in the great difficulty of securing 



ARTIFICIAL HORIZON. 



Instrument by Queen < Co., 

 Philadelphia. 



accurate observations. The lenses and mirrors of the instru- 

 ments are covered with frost from the warmth of the body or 

 the breath, the lubricating oil freezes in the joints, the silver 

 backing of the mirrors cracks and granulates in the cold, and the 

 artificial horizons freeze if liquid, and refuse to stay horizonal 

 if solid. 



Should there be fog or the heavens be overcast, no observa- 

 tions are possible. During the six months of summer daylight 

 the stars are not visible, although the brighest planets might be 



