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150 Scientific Intelligence. 
We know that ice two or three feet or more thick contracts 
very considerably in a few hours by a ae fall of fifteen or 
twenty degrees of temperature. I have found cracks in Lake 
Winnipeg three or four feet wide, betied by this cause during a 
single night, almost poppe our sledge j journey. This gap soon 
freezes up. Then the weather gets milder, the ice expands, and 
with the new additional foiantion is too large for the lake, and is 
forced up into ridges. This process goes on at every ‘cold snap,” 
nagar with milder weather. Now supposing a glacier for 
ten or more feet - its depth. contracts by cold, as lake ice is 
known to do, it will get a series of cracks probably in its longest 
axis, say from inland seaward; the first suowdrift will ‘fill up 
these cracks or some o ce ina this filling up will to some ex- 
tent perform tl ©) as the freezing “of the cracks in the 
the glacier, but as this expansion would naturally tend downhill, 
instead of up, the whole motion would be downwards. But even 
the cracks I mention did not take place, the contraction by 
cold would pull the ice downhill, not up, while the expansion by 
increase of temperature would tend to push the glacier downhill, 
so that these opposite actions would produce similar effects in 
rae the glacier, or such part of it as could be acted upon by 
external temperature, downwards. 
I may also add that when a crack, however slight, is formed b 
contraction, the eae is admitted into the body 0 of the glacier, 
” 
will be vonbinbornd that Professor Agassiz’s theory of glacier 
isthe makes the dilatation arising from the freezing of the 
water that descends into the glacier the chief cause of motion. 
In his Geological Sketches, published in 1866 (p. 280), he states 
hat other causes of motion have acted, but rstill urges that 
dilatation of the mass resulting from ‘the freezing of infiltrated 
water was an important means. 
3. Glacial cold. ie? the Geological Magazine for July, Mr. S. 
. Woop reviews bricfly the facts with regard to the ice of the 
ice period, and the views as to glacial cold, and apne the 
opinion he had ebony: Lobes that the period was “due 
neither to a change in the earth’s — a to any rataaon in the 
eccentricity of the earth’s or orbit t, nor to any change in the distri- 
bution of land and water, but to a acied: in the heat-emitting 
power of the sun.’ 
; Couebulions to the History of Lake Bonneville ; by G. K. 
Gusert. Ann, Rep. U. 8. Geol. Survey, 1880-81, pp. Lies , 
with plates and maps.—This paper is an abstract of Mr. 
full but yet ri birceera Report on Lake Bonneville. Haslier 
contributions by him on the lake and its outlet are contained in 
volumes xv (1878) ial xix (1880) of this Journal. The present 
paper relates prominently to climatic changes which the phases ee 
the lake indicate ; the mequality in change of level undergone _ 
