416 
THE GEOLOGIST. 
see ^vhy the t]ieoi7 of the " non-protusion" (if I may so call it) of eranite 
should not be regarded as very plausil)le ; but if, ou tlie otiier h;uid, instances 
have been discovered, then I shoidd think the idea must fall to the ground, 
unless the facts can be accounted for ui any other reasonable manner. 
1 am but a youn^i; geolo_"-ist, and therefore not thoroughly versed in all the 
details and intricacies of tuis most interesting science ; b\it tliis is a subject 
upon which I shoidd be very glad to obtain some information- — Yours, &c., 
Edmund St. Aubyn. — Granite has always been regarded by ii\odern geologists 
as a crystalline rock formed under great pressure in the depths of the earth. 
Mr. Sorby has written some excellent i)apcrs ou the evidence of tlie presence 
of heated water in the changes effecting the transmutation into granite ; and iu 
tiie elementary works of Sir Charles LyeU and otliers, diagrams are given illus- 
trative of the manner of tlie metamorphosing action, which display also how 
the lowermost or deepest granite nnist oc the most recently formed. 
No evidence Avliatever, so far as we know, exists of the over-r\iu or out -flow 
of granite like a lava-stream. Such effluxes of volcanic matter are found in the 
form of bedded tra])-roek, basalt, &c., all of whicli have been ejected from an 
orilice or chimney of eruption. Not so granite, which is boss-like and, probably 
even, only ordinary sedimentary rock changed or altered by the uprise of the 
range of the isothermal lines of tlie internal heat coiLsequeut on the stopping 
out, by the deposition in the ancient ocean-basins of thick masses of sediment, 
of the conductive action of the ocean-water on the principle pointed out in the 
article on " Connnon Fossils," at page 15A of the present volume of tliis 
^Magazine. 
The action of lieated water combined with pressure is accounted for in the 
consequent heating, under sueli circumstances, of the infiltered water always 
met with at great deptlis. The principal cvidenec brought forward l)y Mr. 
Sorljy on tliis point is the presence in grauite-rock of small cavities jiartly filled 
with water, the cxjilanation of which is, tiiat being originally bubbles of hot 
water or steam, as the cooling of the granite took place, these contracted in 
dimensions, leaving the cavities only partly filled with globules of the con- 
densed fluid. 
The continued heating and expansion of the lowermost rock-masses or other 
causes and actions may have caused a protrusion of the upper and solidified 
])ortion of a granite-mass, Lu some rare or doubtful cases, but such a fact woidd 
in no way militate against the general doetrme of the graduality and pro- 
fundity of the grauitizmg operations. 
FOKJIATION OF MlNEK.\L VeIKS BY SiMPLE SEDIMENTARY DEPOSIT. — SiR, 
• — The exceUent piiper on the deposition of strata in your Ajiril number, show- 
ing how unnecessary it is to refer to any other cause than the natural shoal 
formations, the different complicated appearances of horizontal and perpen- 
dicular strata leads me to ask if mineral-veins have not had the same origin ? 
1 mean, have they not Ijccn laid down in fine seams perhaps on sloping shoals ere 
they or the beds containing them were fused and crystallized by volcanic agency ? 
Prom wliatever source the minerals themselves were derived — and we know 
that silver, copper, &c., arc finely diffused in the sea — there is nothing impro- 
bable in the idea that they may have been strewed over a muddy or sandy 
shore, as the ease maybe; and no one can walk along a rock interstratiiicd with 
quartz, &c., without coming to the conclusion tliat in this way came into its 
present position. The ores and various metals they contain ajipcar to me to 
have been alike dejiosited in thin layers at intervals amongst the other dcbria. 
May I also trouble you to tell me what yon consider the best authority to 
consult uj)on Infusoria ? Also on the formation of fossils, as I believe the cir- 
cumstances under whicli the latter were produced must have been extremely 
rare : for iustance, iiad the shoal of Saud-launces mentioned by Dr. Dawson 
