TO STRyVTIFIED ROCKS. 
41 
ch the common consent of nearly all modern 
geo ogists and chemists refers to the action of 
re. he agency of central heat, and the ad- 
mission of water to the metalloid bases of the 
ear s and alkalis, offer two causes which, taken 
sing y or conjointly, seem to explain the pro- 
uction and state of the mineral ingredients ‘of 
lese rocks ; and to account for many of the 
grand mechanical movements that have affected 
tne crust of the globe. 
The gradations are innumerable, which con- 
nect the infinite varieties of granite, syenite, 
porphyry, greenstone, and basalt with the tra- 
chytic porphyries and lavas that are at this day 
ejected by volcanos. Although there still re- 
main some difficulties to be explained, tliere is 
litt e doubt that the fluid condition in which all 
nnstratified crystalline rocks originally existed, 
whosTef? solvent power of heat 5 a power 
»hose effect .„elti„g the most solid materials 
lardes. « “■« “f 'he 
glass.* ^ materials of 
fl'im °** f f''. “» laaliei cooled 
ficial crystalline rn l" f James Hall, on reproducing arti- 
'decent experiiLn! pressure; and the more 
artificial crystals I - f ^'tscherlich, on the production 
ponent element L proportions of their com- 
once uroed , '"“y objections, which 
""d against the igneous origin of crystalline rocks. 
