PERMANENTLY FROZEN SUBSOILS. 255 



" the depth to which in Northern countries the summer thaw 

 penetrates, varies with the nature of the soil, but except in 

 purely sandy, and very porous beds, it nowhere extends two 

 feet deep in American and Siberian lands, lying within the 

 Arctic Circle." * 



So far north as Spitzbergen, this would probably 

 be reduced to quite one-half, for at the end of July 

 or early in August, 1881, at Jockmock in Swedish 

 Lapland, only a very short distance within this circle, 

 we found the frost still prevailing in great intensity, 

 rather under than over this distance beneath the 

 surface; and were informed by residents, that it never 

 disappeared from the soil at that depth. The subsoil 

 of arctic lands therefore remains in a permanently 

 frozen state, and if it was not for the perpetual presence 

 of the sun above the horizon in these regions, for a 

 period of some eleven weeks during the summer season, 

 it is probable that almost every kind of vegetation 

 would slowly perish; but the prevalence of endless 

 day, during this period, has the effect of so stimulating 

 the growth of plants, that it proceeds by both night 

 and day throughout the whole of this time with 

 extraordinary rapidity and this to a certain extent 

 makes up for the exceeding shortness of the season. 

 But the moment the nights begin again, the descent of 

 the solar disc beneath the horizon, even for an hour 

 or two, is instantly followed by a rapid fall in the 

 temperature; and a short but intense interval of cold 

 sets in, which is but tardily removed by the reappearance 

 of the great luminary of the day, whose early rays, 

 in these far northern regions, have but scant power 



* Zoology of the Voyage of H.M.S. Herald, by Sir John Richardson, 

 Edited by Professor E. Forbes, F.R.S., 1854, p. I. 



