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ence to the constitution of granite, if you take separate crystals, you will also 
find that each crystal has a certain proportion of water chemically or minera- 
logically combined ; and if you drive it out, the crystal becomes opaque, and 
loses weight, the quantity varying from two or three to twenty per cent. 
Without water, crystals are not formed, especially rock-crystals. Again you 
may have granite, with gold in saturation. In another place you will find 
the gold becoming gradually developed out of the granite as the granite under- 
goes changes, and coming out like large round balls. Elsewhere you find a 
little gold in dissemination, but not like the other. There is change constantly 
going on ; the condition of the rocks is never stationary, but it either changes 
into lamination, or into fractures, something like the bark on the trunk of a 
tree. Now, I say we have such an immense accumulation of facts, that we 
ought now to insist upon facts ; and not go on trying to find out what is in 
the centre of the earth, and so on. Let us attend to facts as we find them, and 
see what we really have ; and let us leave theories for the future. I will add 
one or two words with regard to minerals. I have no hesitation in stating 
that I will go to any rock and say what it contains by looking at it. If you 
let me see a good surface of it, I will state whether it contains gold, silver, 
tin, and so on. I am speaking as to the metal the rock will contain, and 
not as to the quantity of the metal, for that will depend on the amount of 
deposits and accumulations, but I am referring only to the nature of the 
constituents. 
The Chairman.— I shall only make a few observations from my own point 
of view, in confirmation of what Mr. Hopkins has said with regard to the 
formation of granite. In doing so I may express some of my objections to 
the theory advanced by Mr. Thompson. The experiment performed by the 
latter gentleman on a small scale, as Mr. Hopkins has reminded us, is wrough 
out by nature on the most gigantic scale. Wherever we find active volcanoes, 
we find them melting granite, or some other primary rock. Lava, obsidian, 
pitchstone, and such-like volcanic products, are but molten primary rocks. 
Now I ask what analogy do any of these substances bear in their structure 
to the so-called primary rocks ? Are they anything like granite, for instance ? 
Mr. Thompson admits that the structure of granite could not be formed 
from any of these substances by slow cooling. That I take to be an im- 
portant admission. I cannot believe it is produced by quick or any inter- 
mediate rate of cooling. We have not to go far even in London for a practical 
demonstration of the structure of the primary rocks. Our bridges and public 
buildings show us that granite is composed of well-formed crystals of several 
distinct minerals, interlacing one another in every direction crystals of 
quartz, mica, and felspar. On London or Southwark Bridge you may see 
crystals of the latter substance as large, or larger, than your hand, presenting 
to the casual observer the appearance of large fossil bones. The constituents 
of granite not only contain water chemically united to them, but they also 
contain water mechanically diffused,— a fact which can hardly be reconciled 
with their production by crystallization from a molten mass. Now let us 
consider the crystalline constituents of granite — we have crystals of quartz, 
