252 T. S. Hunt on Lithology. 
vapor, it remained, as we have seen, to take its part in the crys: 
tallization, in some cases forming hydrated minerals; and the 
excess of it, as Mr. Sorby suggests, passed up as a highly heated 
liquid, holding dissolved materials, which would afterwards be 
deposited in the form of mineral veins in the fissures of super: 
incumbent rocks. : 
I have thought it well to give at some length the remarkable 
results and conclusions by Mr. Sorby, because I conceive that 
they have not as yet received the full degree of consideration to 
which they are entitled, and are perhaps little known to some 
my readers.’ The temperature deduced by him from the exam- 
ination of the crystals of hornblende and feldspar from Vesu- 
vius is curiously supported by the experiments of Daubrée ; who 
obtained crystallized pyroxene, feldspar and quartz, in presence 
of alkaline solutions, at a temperature of low redness; while De 
Senarmont crystallized quartz, fluor-spar and sulphate of barytes 
in presence of water, at temperatures between 200° and 300°C, 
At the same time the deposits from the thermal waters at Plom- 
biéres show that crystalline hydrous silicates, such as apophyllite, 
harmotome, and chabazite, have formed at temperatures but little 
above 80° C. 
We conceive that the deeply buried sedimentary strata, under 
the combined action of heat and water have, according to their 
rent beds. It is only those rocks which, like lavas, have — 
ssimilar 
to those of the undisturbed crystalline sediments. With this ex- 
ception the only distinction which can be drawn between strati- 
- fied and unstratified masses must in most cases be based up 
rocks, or sediments displaced and translated, forming — 
and intrusive masses. Under the head of exotic rocks 18 ei 
ever to be included another class of crystalline aggregates, whit 
are for the most distinguished by their structure from 1) 
jected or intrusive masses. I refer to the accumulations which 
© Sie taster bales ing those of Sorby, Pree. 
Kip. dan Peetton, Moras 13; 1863; had Snot ye Geol. Soc., Vol 
