218 CLIMATOLOGY. 



above the sea, the frost towards the close of winter had 

 penetrated three and a half feet in a cultivated field, while 

 in the woods not above six inches of soil Avere frozen. No 

 search was made for a frozen substratum. These are the 

 chief observations * I have been able to collect, having 

 reference to this subject. It is plain that much more ex- 

 tensive researches are required to enable us to form any 

 general conclusions which can be relied on. 



Professor Baer informs us that in Europe and Siberia, 

 the farther we go east, the more southerly do we find the 

 limit of perpetual ground ice to be. In the environs of 

 Lake Baikal, ice remains at least in one locality all the 

 year. No permanent ice was found at Tobolsk in lat. 58° 

 N., but Humboldt discovered small pieces at the depth of 

 six feet in summer in the elevated district of Boguslowsk, 

 near the foot of the Ural Mountains, in lat. 59° 45' N. 

 It would appear from these instances that the ground ice 

 has a more southerly limit on the shores of Hudson's 

 Bay than in Siberia ; and that in America, as far as obser- 

 vations go, that limit follows the course of the isothermal 

 lines which dip to the south as they proceed to the east- 

 ward. 



THERMOMETRICAL OBSERVATIONS IN THE VALLEY OF 

 THE ST. LAWRENCE. 



The subsequent tables of temperature and notices of 

 the progress of the seasons are arranged so as to convey, 

 as far as my materials go, a view of the climates of the 

 successive lake basins from the St. Lawrence northwards. 

 Table II. is intended also to illustrate the fact that the 

 climate, on the west side of the continent, is milder than 



* All the experiments made in Rupert's Land, in 1835-36, are 

 detailed in the Ed. New Philos. Journ. for January 1841. 



