[ 6 3 .] 
large ; bat where the flow of moifture is flow, tuei>- 
(the outfide Surfaces, and indeed the whole maSs, 
becoming hard before a frefh fupp’iy of Salts is addeu) 
the ftones will be Small. And again, where the 
moifture and faits pafs through large pores, theie tne 
cryftal, or fpar, or other concretion, will be very 
imperfect, being mixed with much heterogeneous, 
matter; but where, the moifture., .and cryftallizing 
particles, or faits, defeend though very minute pores 
there the faits will be moft unmixed and pure, and 
the cryftal or ftone will be of the moft transparent 
kind In fhort, I cannot but look upon the largeft 
caverns in the earth, and the fmalleft cavities in ftone, 
as producing fimilar effects, and therefore co.nfideL 
them in the fame light. 
In thefe conclufions I may perhaps be mittalcen, 
but they are at leaft; confiftent with the observations 
we make : for wherever there are cavities in the earth,, 
or in ftones, into which moifture can any way delcena, 
we almoft always find thefe kind of cryftallizations 
and concretions ; and the more plentiful the moifture 
is, and the more porous the ftrata of earth or ftones 
are through which it pafles, the larger the concretions 
are, and the more remote from a tranfparent ftate.j as 
appears in thofe great caverns in the Peak, and in 
Somerfetfhire, &c. Whereas, on the contrary, the 
harder and lei's porous the fubftance is through whicn 
the moifture paffes, the more transparent are the 
ftones formed by it, as in the cafe of Briftol ftones, and 
of feme of thofe beautiful fpars adjoining to veins of 
^Whether all kind of ftones may not be formed m 
Somewhat the fame manner, by the water carry mg 
