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Aut. XX. — On the Geognostical Relations of Granite^ Quartz- 
Rocli, and Red Sandstone. By Professor Jameson. Com- 
municated by the Author. 
1 . 
Granite^ which is a very abundant and widely distributed 
rock, is a compound of felspar, quartz, and mica, disposed in gra- 
nular distinct concretions of various magnitudes and forms. 
These concretions, at their line of junction with each other, 
present appearances which are highly interesting in a general 
geological view. Frequently the concretions are simply attach- 
ed to each other, or they are intermixed at their line of junc- 
tion, the felspar being intermixed with the quartz, the quartz 
v/ith the mica, or the mica with the felspar ; and not unfre- 
quently branches or veins shoot from the one concretion into 
the other. These phenomena, thus distinctly seen in the small 
scale, are of the same general nature with those observable at 
the lines of junction of gneiss, granite, mica-slate, porphyry, 
limestone, trap, and other rocks. 
Quartz-Rock^ which is principally composed of granular con- 
cretions of quartz, with a little disseminated felspar, and a few 
scales of mica, when particularly examined, exhibits the same 
kind of structure as that just described as occurring in granite. 
Red Sandstone"^. — This rock is principally composed of fine 
granular quartz, with a considerable portion of felspar and a little 
mica, disposed in granular distinct concretions, presenting at their 
junctions the same appearances as in granite and quartz rock. 
2 . 
Mineralogists in general admit the chemical nature of granite, 
but deny that quartz-rock and its sandstone have been formed by 
deposition from a state of chemical solution, the characters of these 
rocks, in their opinion, intimating a mechanical formation. But 
on what data is this opinion founded ? The general arenaceous 
* This red sandstone differs from that which lies immediately below the coal for- 
^[nation, as will be explained in a future paper. 
