122 Dr Richardson on the Frozen Soil of North America. 



turn of seventeen and a half feet of perpetual frost. It may, however, be 

 material to remark, that, on close examination, the total depth of the pit 

 was found to approximate very nearly to the height of its mouth above 

 high-water mark in its vicinity, which may lead to a suspicion that the 

 layer of permanent frost might have been thicker had the river bank been 

 higher at the place where the pit was dug. The " blue mud" above no- 

 ticed was found to extend to the lowest point reached, varied at points 

 from three to five feet asunder by layers of small gravel mixed with solid 

 ice. Each layer about from three to five inches thick. Shells, such as 

 are still found about the shores of the stream, were discovered imbedded 

 in the mud about twelve feet from the surface in a state of perfect pre- 

 servation ; pieces of drift-wood (willow) were dug out about nine feet 

 deep, some of them quite fresh. The temperature of the thawed mud 

 immediately below the permanent frost was ascertained by repeated 

 trials to be + 33° on Fahrenheit's scale. 



" A similar attempt was made last autumn to ascertain the like facts at 

 Severn outpost ; but, from various adverse circumstances, the result was 

 not so satisfactory. The first pit was dug through a loose sandy soil, 

 eleven feet deep, at which point the permanent frost was reached. The 

 surface-water, however, filled the pit, and the party being unprovided 

 with adequate means to keep it dry, another attempt was made elsewhere. 



" In this second pit, the labours were again interrupted by water, after 

 having dug through seven feet of thawed ground without reaching the 

 frost. A third attempt was made in a close compact soil of blue mud, 

 about twenty yards from the bank of Severn river, in which they reached 

 the permanent frost at the depth of 5f feet from the surface. The labour- 

 ers continued cutting the solid frost to an additional depth of 7i feet when 

 the surface-water, together with a snow-storm, put a stop to further pro- 

 ceedings that season. 



"The postmaster, who superintended the undertaking at Severn, men- 

 tions that, having occasion to cut into the river-bank (which at that place 

 was above thirty feet in perpendicular height), for the purpose of making 

 a summer quay, he found the frost extending downwards till it reached 

 the mark of high water, below which the earth appeared quite soft and 

 thawed, as far, in a horizontal direction below the frost, as he could pe- 

 netrate. This circumstance appears to coincide with what was observed 

 at York Factory, and to lead to the conclusion that permanent frost de- 

 scends to the point where it first meets with the level of water." 



No. 9. — Extract from a Letter from Mr Chief-Trader Murdoch 

 M c Pherson, dated Portage la Loche, 4th August 1836. 



" A copy of a letter from Dr Iviehardson to Governor Pelly, dated Mel- 

 ville Hospital, 25'ib February 1835, was transmitted to me, together with 

 instructions from Governor Simpson to furnish the information required ; 

 but I am sorry to inform you that those instructions did not reach me till 

 late in December, when the ground was so deeply frozen that experiments 



