Ou JOURNAL OF THE PLYMOUTH INSTITUTION. 
as in the cliff of the Dewerstone. Little wonder, then, that the 
elder geologists inclined to the belief that granite was really 
stratified ; or that unscientific observers, gazing upon such a grand 
example of mural jointing as the the rocky crown of Pew Tor, 
should assign it an artificial origin, 
This jointing, or fissuring, dates back to the time when the 
granite was cooling and contracting (for I have no doubt what- 
ever that our granite was once in a fluid and highly-heated state) ; 
but its initial character has been greatly modified and enhanced 
by atmospheric action. Granite is so hard, and to all appearance 
so enduring, that its power of resisting the waste of wind 
and rain and frost, and the disintegrating operation of vegetation, 
is commonly overestimated. A good deal depends upon the 
texture. The fine-grained, compact granites have high resistile 
powers, but the coarser crumble away with comparative ease. To 
weathering our granite groups owe such characteristic outlines as 
those of the Cheesewring, or Bowerman’s Nose. The basins once 
attributed to the Druids were chiselled by wind and rain. The 
huge chaotic carpetings of blocks, which form the “clitters” of 
the tors, were probably detached by frost. How speedily weather- 
ing will progress under favourable conditions, a fact observed by 
myself in the quarry at Trowlesworthy Tor will indicate. From 
a joint face, left solid when the quarry was worked at that point, 
probably about twenty years previous, a peel of granite an inch in 
thickness, but several feet in superficies, had been so completely 
detached from the parent mass that the introduction of a stick 
sufficed to bring down the whole. The fissure thus widened was 
no doubt quite imperceptible when the quarry was abandoned, but 
still it was there, and year by year the percolation of the water, 
and the repeated expansion of frost, widened it to such an extent 
that my stick could have hastened the end by a very short time 
only. lichens and mosses also play an important part in the 
process of granitic disintegration, but they in return protect the 
rock from the ordinary weather influences. 
The varieties of local granite are very numerous, as the study of 
the bed of any of our moorland streams will show. Those which 
have been chiefly worked for commercial purposes, as at Hey Tor 
and King Tor, are porphyritic, from the appearance of large 
erystals of felspar. The King Tor granite is a good, compact 
stone, fairly even in texture, regular in colour, and with ex- 
