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most important, (at least to the geologist,) acting through the 
medium of heat, chemical combination, and crystallization. 
The state of our knowledge of these, as a branch of physics, 
is scanty and deficient, and was presented in the form of five 
tables, shewing— 
Ist. Bodies known to expand in volume by combination. 
2nd. Bodies known to expand in volume on changing 
their state of aggregation or arrangement. 
Srd. Bodies known to contract in volume in combination. 
4th. Bodies known to contract in volume in changing their 
state of aggregation or arrangement. 
5th. Bodies whose volume is known to remain unchanged 
in combination. 
After stating that these tables were only brought forward 
as indicative of the class of forces proposed being treated 
of, and pointing out some of the very singular facts which 
they contain, of alteration of volume, and the immense force 
with which it frequently takes place, the author proceeded 
to apply the results of his own experimental determinations, 
of change of volume, in solutions of chloride of calcium 
and sulphate of soda, on mutual decomposition, and of the in- 
termediate oxide of iron in passing to peroxide—to the salt 
formation of England—and shewing, that if considered as a 
chemical deposit, an elevation of the surface, of eight feet 
six inches, will have been produced, by reason of this change 
of volume only. 
A case of observed expansion in volume, by further 
oxidation of the blue marl, of the saliferous system, and 
its remarkable effects, was brought forward, and analogy 
shewn with the indurating marl forming the bottom of Lake 
Superior. The effects of these swellings, in all directions 
of a mass, in producing consolidation and integration of its 
parts, is there pointed out. 
The author then proceeds to apply this principle, to ac- 
count for the formation of the contemporaneous quartz veins 
