30 JOURNEY TO THE SHORES 



dional altitude when the thermometer stood at 46*^ 

 below zero, at the imminent hazard of having his 

 fingers frozen. 



He found the sextant had changed its error 

 considerably, and that the glasses had lost their 

 parallelism from the contraction of the brass. In 

 measuring the error he perceived that the di- 

 ameter of the sun's image was considerably short 

 of twice the semi-diameter ; a proof of the uncer- 

 tainty of celestial observations made during these 

 intense frosts. The results of this and another 

 similar observation are given at the bottom of 

 the page*. 



altitude of O upper limb was 2° 52' 

 ■—45° 5'. By comparing this altitude, 

 ;tion and parallax, with that deduced 

 observed in autumn the increase f 

 V^ ^' i^'}^' r^^'' '^f^^'^^on, therefore, for the 

 1 IS 21 49 . Admitting tliat the refraction in- 

 ^...«.o ,^ u,c same ratio as that of the atmosphere at a mpan «tat<. 

 of temperature, the horizontal refraction wiU be 47' 22" R„7th! 

 diameter of the sun measured unmediately alter t^e obs^rv'ati 



:nd^t;Jl!=?^!f?-"^^^ 



lu ti.c aoove-mentioned ratio, is 53' 3" at th^ f^.v, 

 . So that in the parallel 680 42'. wht; if LlZ'^^^^f ' 

 je sun would be mvisible for tliirty-four days, his unner limh wl 



