Dr Richardson on the Frozen Soil of North America. 121 



weather, for the distance of about three miles in the circuitous course it 

 takes to Net Point. This is supposed to be the leading channel to the 

 main river, but no current is perceptible ; the open water must therefore 

 be caused by the nature of that part of the bed of the lake, for the cold 

 at times is sufficiently severe to freeze every thing but an actual cascade." 



No. 6. — Extract of a Letter from chief trader Jacob Corrigal, Esq., dated 

 Albany, 3d September 1836. 



" I beg to inform you, that, in order to ascertain the temperature of 

 the earth at this place, we dug a pit in the course of yesterday and this 

 morning, and found the soil thawed at the depth of five feet, and frozen 

 earth three feet seven inches. The soil at the surface six inches deep of 

 black earth, from that and nearly to where the frozen earth terminates, 

 there was a brownish-coloured clay, so hard that it was not perceived 

 to be thawed earth, till after it was cut about two inches deep with a nice 

 chisel. A few small pieces of shells were found amongst the blue clay." 



No. 7. — Extract of a Letter from Mr Chief Factor R. M'Kensie sen., 



dated Isle d la Crosse, 1st June 1836. 

 " Two pits were dug 15th October last. One at Isle a la Crosse, 

 thirty yards from the lake, to the depth of ten feet, when water began to 

 come up, two feet of gravel and sand on the top, and eight of hard clay 

 ground. And one at Green Lake, to the depth of fifteen feet forty yards 

 from the lake, two feet of pure sand, and thirteen of clay ground, but so 

 hard at the bottom that it was impracticable to dig it deeper, and no 

 frozen earth to be found. I have heard it frequently said by old servants 

 who have resided here for upwards of thirty years, and who have had oc- 

 casion to dig pits and graves at all seasons of the year, that they never 

 knew the frost to penetrate into the earth more than from two to three 

 feet deep." 



No. 8. — Extract of a Letter from Mr Chief Trader James Hargrove, 

 dated York Factory, 25th August 1836. 



" At this place the digging of a pit to ascertain the principal facts, 

 commenced in the beginning of October last. The surface water being 

 then completely solid, and any addition to the depth of last summer's thaw 

 being despaired of, as the new frost had already penetrated eight inches 

 into the ground. The spot selected was the driest in the vicinity of this 

 factory, perfectly exposed to all changes of atmosphere throughout the 

 season, and upwards of thirty yards from the bank of the river. The soil 

 is a deep blue tenacious mud. The periodical thaw was soon dug 

 through, and when accurately measured, was found to be exactly three 

 feet from the surface-level to the beginning of the permanent frost. From 

 this point the operation continued for about fourteen days, at the end of 

 which time the thawed earth was again reached, the distance from the 

 surface of the ground being twenty and a half feet, thus leaving a stra- 



