DEPTH OF PERMANENTLY FROZEN SOIL IN THE POLAR REGIONS. 155 



pendently of season, exercises a considerable influence in determining 

 both the rapidity and penetration of the thaw. 



'In venturing to offer some explanation of Sir John Richardson's 

 statement "that the soil was found frozen to a depth of nearly 20 feet at 

 York Factory," apart from the consideration of it being a severe season, 

 which it undoubtedly was (for on referring to old records I find that the 

 winter of 1834-35 was exceptionally severe), I would in all deference sub- 

 mit, from observations of my own upon this point, that the measurement 

 alluded to gave but a section of the lateral freezing of a landslip ; for in 

 sounding the " face " of a perpendicular bank, say 40 feet in height, for 

 frost-penetration, the frost will be found at its depth in relative proportion 

 to the height of the bank, making all due allowance for the varying of its 

 penetrative action in differing strata ; but if the bank be not perpendi- 

 cular, but sloping, the frost follows the decHvity, and a portion of the 

 thawed surface (probably due to heavy rains) slides over the frozen sub- 

 soil, and, impinging on the denser structure, abruptly breaks off at the 

 point where the frost-action is checked, and gliding on thus exposes a 



Rough Diagram of Landslip in Hayes River : apparent frost-penetration of over 14 feet 

 proved to be only 4 feet. 



thawed surface, leaving a deceptive frost-line far below the true one, which 

 upon a cursory examination leads to the supposition that the ice-pene- 

 tration is greater than it really is. Though this is conjecture as regarding 

 the statement in question, I have the rather endeavoured to illustrate not 

 only what I have witnessed myself, but that which may be an explanation 

 of the depth of frost alluded to in this particular instance.' 



' But in further reference to Sir John Richardson's statement " that 

 the soil was found frozen to a depth of nearly 20 feet at York Factory," 

 I must not omit the fact that Mr. George Gladman, a chief factor of the 

 Hudson's Bay Company's service, in his evidence before the Select Com- 

 mittee of the House of Commons in 1857, says, "Pits were dug there 

 (York) with a view of ascertaining the depth of ground thawed during 

 summer ; repeated diggings showed about three feet of thawed ground, 

 whilst the perpetually frozen ground was found to be fifteen feet deep." 

 In this connection, although fully admitting its corroborative force, I 

 cannot but point out a discrepancy of nearly five feet (4 feet 10 inches) 



' It is to be observed of the above diagram that if the line of fracture, instead of 

 being only some four or five feet back from the edge of the bank, had been twice or 

 thrice that distance, the whole frozen part would have disappeared and the section 

 have disclosed the real depth of the frost, provided the slip occurred, as they usually 

 do, at a period of the year too advanced for the new face to freeze to any depth. 



