Affinity between Bafaltes and Granite . 61 
broke out through the granite ; and in others, is at pains to 
fhew, that thefe fubftances are not thoroughly blended, as in 
the laft example, and in that defcribed by Ferber. 
It may be faid, and no doubt it fometimes happens, that 
(hivers of granite, broken off by the violence of explofion, 
are licked up by melted matter as it moves along; thus, m 
volcanic breccias an older lava is inclofed in one more recent, 
and thus what is called primary is fometimes encafed in fecon- 
dary granite. But fuch an hypothefis is too narrow to embrace 
all the phenomena. It does not explain the incipient coagula- 
tion of the uniform pafte into grains, and thofe the different 
grains of granite; nor the ditfufion of the conftituent paits of 
granite through the fubftance of bafaltes ; nor the fifth fpecies 
defcribed by Mr. Ferber. 
In the whinflone rocks of England, which are far more 
numerous than is commonly fuppoied, I have frequently ob- 
ferved in the fame hill, i. homogeneous dark grey ftone ; 2. 
felafpath enclofed in this as in a pafte ; and, 3. the pafte diiap- 
pearing, and the whole becoming granular, and the grains 
heterogeneous. Befides feldfpath, quartz is found in innu- 
merable maffes of varying magnitude * in many whinftone 
rocks, and as proper bafaltes is but a confufed mafs or cryftals 
of fhoerl, we have all the ingredients of granite ; and why 
* In the Wrekin, Cader Idris, &c. numerous and large veins filled with 
quartz occur; but thefe have not been fecreted from the fubftance of the rocks 
in which they lie. They, perhaps, fliew this molt filiceous ingredient of granite 
to have been near and in fufion at the fame time. About Cader Idris I fufpeft an 
incorporation of granite and bafaltes may be found. I have feen pieces of granite 
about that mountain which did not feem to have been far removed from the rock 
to which they belonged ; but I had then no particular inducement to make am 
accurate examination. 
mav 
y 
