INTERESTING SCIENTIFIC WORK IN THE ARCTIC 213 



astronomical observations, and greatly multiply them. The 

 best instrument under such conditions is perhaps a small theo- 

 dolite, as used by Captain Scott in the Antarctic. This instru- 

 ment is steadier than a small sextant, which has to be held in 

 the hand, and probably more accurate. 



"The readings of altitude of the sun should be checked, if pos- 

 sible, by another member of the party, and carefully noted in 

 the traveler's field book or diary, with a record of the tempera- 

 ture at the time and the barometric pressure, so 

 that corrections may be applied for these two 

 influences. The altitudes should be roughly 

 worked out on the spot to indicate how closely 

 he was approaching to the Pole. Having 

 reached what he believed to be the position of 

 the Pole, he should be careful to take a very 

 large number of different altitudes over a 

 period of hours, or even days, and the mean of 

 these observations would undoubtedly give him 

 a fairly accurate result. 



"These original notebooks, absolutely un- 

 altered, and the testimony of his fellow-travel- 

 ers, are practically the only evidence he could 

 produce of having reached the Pole. If he 

 possessed a camera, it might be of some value, 

 if he were on perfectly level sea-ice, to take a photograph of the 

 sun showing the horizon line below. The phenomena at the South 

 Pole would be identical, excepting that the sun would be always 

 in the north, and all lines would lead north, and the dates of the 

 sun's visibility would be reversed namely from September 22d to 

 March 2ist; the maximum altitude of the sun being reached on 

 December 22d. The south-seeking end of the compass would point 

 north in the direction of the South Magnetic Pole." 



While not indispensable to an explorer, there are several other 



POCKET COMPASS. 



Instrument "by Queen & 

 Co., Philadelphia. 



