THE HEART OF THE ANTARCTIC 



mometers any credibility at all was to test them constantly 

 in comparison with a mercury thermometer, which was 

 itself tested occasionally in melting fresh-water ice. 

 Fortunately we had half a dozen mercury thermometers, 

 taken for other than meteorological purposes. Unfortu- 

 nately they were only graduated down to zero (Fahr.). 

 Had the scale gone down to near the freezing-point of 

 mercury, they might have served for all our observations. 

 Whenever a series of temperatures (as in a shaft sunk 

 through the ice) came partly below and partly above zero 

 (Fahr.), the whole series was taken with spirit ther- 

 mometer, but every one above zero was repeated with a 

 mercury thermometer, and the whole series corrected in 

 correspondence with its readings. This practice at least 

 minimised the chance of change in the error of the spirit 

 thermometer, by allowing the least possible time for it. 



In the meteorological screen a mercury thermometer 

 was hung beside the spirit one used for the dry-bulb read- 

 ings. No variation was ever detected in this one, which 

 was undisturbed. The maximum and minimum frequently 

 went wrong, and had to be corrected by observing the 

 position at which they rested when shaken down. 



Greely remarks on the unreliability of spirit ther- 

 mometers. It is desirable for polar expeditions to be 

 provided with mercury thermometers graduated down as 

 low as possible. We have no reason to believe that our 

 thermometers were not of excellent quality. The defect 

 is inherent and largely due to climate. 



CLOUD FORMS 



By JAMES MURRAY 



Without treating them from the meteorological stand- 

 point, some notes and sketches of the more striking forms 

 of cloud associated with Mount Erebus may be of interest. 



418 



