250 T. S. Hunt on Lithology. 
The presence of water in igneous rocks, and the'part which it 
may play in giving liquidity to all volcanic and plutonic rocks 
was insisted upon by Poulett Scrope, so long ago as 1824, in his 
Considerations on Volcanos, (see also Quart. Jour. Geol. Soc. Lon- 
don, xii, 341.) This view has since been ably meets 
Bu eol, 
hate tassium, sodium, calcium and magnesium, so 
times with free chlorhydric acid. Similar fluid cavities were 
oun im in most crystals artificially formed in aqueous s0- 
merous small fluid-cavities. In like manner, he deduces rom 
the fluid-cavities in the Vesuvian minerals just noticed, a tetr 
perature of from 360° to 880°C. The presence, at the same HMé, 
of bubbles or vapor-cavities and of glass and stone-cavitles In 
tion was present, along with melted rock, and various gases 47 
vapors. * * * * I therefore think that we must conclude 
visionally, that at a great depth from the surface, at the foci 
