NATURAL HISTORY. 



555 



sited, without a possibility of add- 

 ing to a limited depth of saow. 

 Now this would assuredly be the 

 case, if nothing more than the 

 same moistvire evaporated from 

 the snowy surface of ice were 

 again deposited. But, it must be 

 observed, that notwithstanding 

 Avinds from the north, east, or 

 west, may not furnish any con- 

 siderable quantity of snow ; and 

 that although those warm and hu- 

 mid storms which blow from the 

 south, may afford a large propor- 

 tion of their humidity to the ex- 

 terior ice ; yet, as the temperature 

 of the northern regions would be 

 gradually elevated by the long 

 continuance of a southerly gale, 

 the advance of the wind must in 

 consequence be farther and farther 

 before it be reduced to the tempe- 

 rature of the ice ; and, therefore, 

 some snow would continue to be 

 precipitated to an increasing and 

 unlimited extent. 



Hence, as winds blowing from 

 the north must be replaced by air 

 neither colder nor less damp, and 

 as every commixture with warmer 

 streams must produce an increas- 

 ed capacity for moisture 5 there- 

 fore no wind can occasion a de- 

 traction of vapour from the cir- 

 cumpolar regions : on the con- 

 trary, as the snow deposited on 

 the interior ice by southerly 

 storms, (from the nature of the 

 circumstances), must be derived 

 from evaporations out of the sea ; 

 it is evident, that there must be 

 an increase of snow in the icy la- 

 titudes, and that we cannot jjos- 

 sibly determine any limit beyond 

 which it may be affirmed that no 

 snow can be dqjosited. 



3. On approaching a pack, field, 

 or other compact aggregation of 



ice, the phenomenon of the ice- 

 blink is seen whenever the horizon 

 is tolerably free from clouds, and 

 in some cases even under a thick 

 sky. The ice-blink consists in a 

 stratum of alucid whiteness, which 

 appears in that part of the atmos- 

 phere next the horizon. It is evi- 

 dently occasioned thus : those rays 

 of light which strike on the snowy 

 surface of the ice, are reflected 

 into the superincumbent air, where 

 they become visible ; but the light 

 which falls on the sea is in a great 

 measure absorbed, and the super- 

 incumbent air retains its native 

 ethereal hue. Hence, when the 

 ice-blink occurs under the most 

 favourable circumstances, it affords 

 to the eye a beautiful and perfect 

 map of the ice, 20 or 30 miles 

 beyond the limit of direct vision, 

 but less distinct in proportion as 

 the air is hazy. The ice-blink not 

 only shews the figure of the ice, 

 but enables the experienced ob- 

 server to judge, whether the ice 

 thus pictured be field or packed 

 ice : if the latter, whether it be 

 compact or open, bay or heavy ice. 

 Field ice affords the most lucid 

 blink, accompanied with a tinge 

 of yellow; that of packs is move 

 purely white ; and of bay ice 

 greyish. The land, on account of 

 its sno\\'y covering, likewise occa- 

 sions a blink, which is yellowish, 

 and not much unlike that produced 

 by the ice of fields. 



4. The ice operates as a power- 

 ful equaliser of temperature. In 

 the 80th degree of north latitude, 

 at the edge of the main body of 

 ice, with a northerly gale of wind, 

 the cold is not sensibly greater 

 than in the 70th degree, under 

 similar circumstances. 



5. The reciprocal action of the 



ice 



