418 ON THE CONTRACTION AND EXPANSION OF ICE. 
SOME EXPERIMENTS ON THE CONTRACTION AND 
EXPANSION OF ICE. 
= 
BY J. H. DUMBLE, C.E. 
Read before the Canadian Institute, 10¢h March, 1860. 
ooo 
In the September number of the Journal of the Canadian Institute 
for 1858, I gave a brief statement of facts relative to the expansion 
and contraction of ice, as observed by me on Rice Lake. 
T stated that the contraction and expansion of ice was caused by 
atmospheric changes ; that, up to its melting point, it expands with a 
high, and contracts with a low temperatnre ; that it is susceptible of 
expansion to a much greater extent than of contraction, that when ice 
is equally dense, thick, and glare, and everywhere equally acted upon 
by a heated atmosphere, it expands from the centre towards the cir- 
cumference, and that it expands towards the line of least resistance, &c. 
The observations of another winter, together with actual experi- 
ment, have confirmed the correctness of this theory, with, however, 
one exception. The statement that ice is susceptible of expansion to 
a much greater extent than of contraction, is incorrect. Into this 
erroneous conclusion I was thus led: the expansion of a large field 
of ice, I observed, was manifested by its encroachment on the shores 
of the lake, in which case the ice usually fractured at the ripple mark ; 
wheu, however, the line of fracture did oecur at a distance from the 
shore, it was evinced by the appearance of a vertical ridge, formed by 
the fractured portions of the ice. Such being the case, I naturally 
expected that when the ice field contracted it would shrink away from 
the fracture, whether on the shore or at a distance from it, or else 
that fissures or cracks would be observed somewhere in the ice field, 
of widths commensurate to previous “ shoves.” 
Such evidence of contraction, either the shrinkage from the line of 
fracture, or the existence of cracks or fissures, of widths at all ap- 
proximating to the amount of expansion, was not then observed by me. 
Towards the latter part of last winter I had occasion to cross Rice 
Lake on foot ; the temperature of the previous night had been very 
low. A slight coating of snow lay on the ice, and in it were cracks 
running in every imaginable direction; these cracks penetrated the 
ice and were filled with water, they varied in width from one-eighth 
