Physical Theory of Secular Changes of Climate. 185 



beat enough to melt the snow in such quantities as to produce a 

 river, nor did we find even a stream of fresh water on the whole 

 coast"*. 



Captain Sir James Ross found the perpetual snow at the sea- 

 level at Admiralty Inlet, South Shetland, in lat. 64 c ; and while 

 near this place the thermometer in the very middle of summer 

 fell at night to 23° F. ; and so rapidly was the young ice form- 

 ing around the ship, that " I began," he says, " to have serious 

 apprehensions of the ships being frozen in "f. At the compara- 

 tively low latitude of 59° S., in long. 171° E. (the corresponding 

 latitude of our Orkney Islands), snow was falling on the longest 

 day, and the surface of the sea at 32° J. And during the month 

 of February (the month corresponding to August in our hemi- 

 sphere) there were only three days in which they were not assailed 

 by snow-showers §. 



In the Straits of Magellan, in 53° S. lat., where the direct heat 

 of the sun ought to be as great as in the centre of England, 

 MM. Churrca and Galcano have seen snow fall in the middle of 

 summer ; and though the day was eighteen hours long, the ther- 

 mometer seldom rose above 42° or 44°, and never above 51° ||. 



This rigorous condition of climate chiefly results from the rays 

 of the sun being intercepted by the dense fogs which envelope 

 those regions during the entire summer; and the fogs again are 

 due to the air being chilled by the presence of the snow-clad 

 mountains and the immense masses of floating ice which come 

 from the antarctic seas. The reduction of the sun's heat and 

 lengthening of the winter, which would take place when the 

 eccentricity is near to its superior limit and the winter in aphe- 

 lion, would in this country produce a state of things perhaps as 

 bad as, if not worse than, that which at present exists in South 

 Georgia and South Shetland. 



If we turn our attention to the polar regions, we shall find 

 that the cooling effects of snow and ice are even still more marked. 

 The coldness of the summers in polar regions is owing almost 

 solely to this cause. Captain Scoresby states that, in regard 

 to the arctic regions, the general obscurity of the atmosphere 

 arising from fogs or clouds is such that the sun is frequently in- 

 visible during several successive days. At such times, when the 

 sun is near the northern tropic, there is scarcely any sensible 

 quantity of light from noon till midnight^] . "And snow," he says, 

 " is so common in the arctic regions, that it may be boldly stated 



* Captain Cook's ' Second Voyage/ vol. ii. pp. 232, 235. 



t Antarctic Regions, vol. ii. pp. 345-349. 



% Ibid. vol. i. p. 167. § Ibid. vol. ii. p. 362. 



|| Edinburgh Philosophical Journal, vol. iv. p. 266. 



51 Scoresby's 'Arctic Regions,' vol. i. p. 378. 



