25 
and it liad been feared tbat no successors would be found to carry 
on tbeir work. This apprehension, however, has proved unfounded, 
and it is not probable that any really useful work will drop for want 
of hands to carry it on. 
June 9.—De. Peoctee read a paper ‘‘On SiKca and the Porm- 
ation of Granite,” of which the following is an abstract:—He 
remarked, that as facts in geology accumulate, new explanations of 
them are demanded, and this, coupled with the advance of experi¬ 
mental science, renders many theories at one time universally 
accepted, at the present time untenable, and the object of his 
present paper was to show that the generally received opinion in 
respect to the origin of certain so-called igneous rocks, admitted of 
some doubt. After stating the more general constituents of the 
crust of the earth, silica was said to be one of the most common 
under the form of quartz, flint, &c., and the object of the present 
paper was an endeavour to show that the arguments are stronger 
which give to that substance an aqueous origin than those which 
refer it to the result of cooling from a former fusion by heat. 
Silex exists in two conditions, crystallized and amorphous: the 
former has a speciflc gravity of 2*6, the latter from 2*2 to 2*3. M. 
Senarmont has obtained crystals of Silex by acting upon a solution 
of that substance at an elevated temperature in closed tubes, and 
these crystals were in every respect identical with those of rock 
crystal. The same results have been obtained by other experiment¬ 
alists, but up to the present time all attempts to obtain silica in 
crystals by fusion has failed, for when intensely heated, it runs 
into small globules of an amorphous character, and acquires the low 
specific gravity. Quartz contains a large number of substances 
imbedded in it, and amongst them water and other comparatively 
volatile substances; if, therefore, in the very centre of the crystal 
matter is found which cannot exist at a high temperature without 
being dissipated, the conclusion is justified that rock crystal could 
not have been subjected to a very considerable heat. If Silica is 
supposed to be the product of igneous action, the same difficulty is 
present in explaining the preservation of the ligneous structure in 
silicified wood, the presence of infusoria, &c., in flint, and the 
general fossilization of organic remains. Other arguments were 
then drawn from the pseudomorphic crystals of quartz and the loss 
of water, changes of colour, specific gravity, &c., which varieties of 
that substance undergo by the action of heat. The great interest 
