912 l General Notes. [December, 
low the surface it had a temperature of 28° 5 F. and was barely 
up to the freezing point at three hundred and eighty-two feet. It 
is very different on the American continent. The rare oppor- 
tunity was afforded me by a landslip on a large scale in May, 
1844, of observing its entire thickness near Fort Norman, on the 
Mackenzie river, about two hundred miles further north than 
Yakutsk, and it was only forty-five feet. At York factory and 
Hudson’s bay it is said to be about twenty-three feet. The recent 
extension of settlements in Manitoba has led to wells being sunk 
in many directions, establishing the fact that the permanently 
frozen stratum does not extend so far as that region, notwith- 
standing an opinion to the contrary of the late Sir George Simp- 
son. Probably it does not cross Churchill river, for Sir H. Le- 
froy was assured that there is none at Lake à la Crosse. It de- 
pends in some measure on exposure. 
In the neighborhood of high river banks, radiating their heat 
in two directions, and in situations. not reached by the sun, the 
frost runs much deeper than in the open. The question, however, 
to which Sir John Richardson called attention so long ago as 
1839,is well deserving of systematic inquiry, and may even throw 
some light on the profoundly interesting subject of a geographi- 
cal change in the position of the earth’s axis of rotation. ; 
e Saskatchawan is now navigated from the Grand Rapids, 
near Lake Winnipeg to the base of the Rocky mountains. The 
impediments to navigation on the Nelson river have been found 
to be insuperable, and a company has been formed to make a rail- 
way from the lowest navigable point to the mouth of the Church- 
hill river. 
The land around Hudson’s bay is rising at the rate of five to 
ten feet in a century, The mouth of the Churchill affords far su- 
perior natural advantages for shipping the agricultural products of 
the Northwest territory than York Factory. 
MICROSCOPY .! 
Tue NATIONAL Socreties.—The American Society of Micro- 
scopists, held its third annual meeting at Detroit, on the 17th to 
ioth, of August last, under the presidency of Prof. H. L. Smith, 
of Geneva, New York. Regular morning and afternoon sessions 
were held during the three days; and, in all, fourteen papers were 
read, eight on microscopy proper, and six on natural history sub- 
jects connected with the use of the microscope. Included in the 
latter number is the very elaborate and interesting Presidents 
Address, delivered by Prof. Smith, on the subject of Deep Sea 
Life. A soirée was held in a public hall one evening, which was 
well attended, and was as fully calculated to accomplish its object 
of public entertainment and popular instruction in the powers an 
application of the microscope, as could reasonably be expected 
1 This department is edited by Dr. R. H. Ward, Troy, N. Y. 
