[ 6 + ] 
the ftony particles to the fame place, and their col- 
lecting there together, by their mutual attraction, I 
leave to others to determine j but I am much per- 
fuaded, that this may probably be the manner of the 
production of fpars and cryftals : and perhaps jewels, 
or precious (tones, may grow juft in the fame way ; 
and owe their perfection folely to their being compofed 
of ftill more minute falts, and more (lowly ; whence 
we may conjecture, why it is fo rare to find large 
diamonds. I have 'obferved fome of the Briftol (tones 
to have a fine purple appearance, like an amethyft ; 
and it is well known, that feveral forts of fpars are of 
various beautiful colors, by means of a mixture of 
mineral particles, in which they have a diftant re- 
femblance of jewels j and indeed they feem to be 
very analogous to them in many refpeCts. 
After all, however, I am fenfible that what I have 
advanced deferves not to be confidered as any thing 
more than mere guefs. I know that a confirmation of 
the truth of thefe conjectures muft depend upon ex- 
periments, which I have it not in my power to make: 
and I can only conclude with wishing, that fome gen- 
tlemen, converfant in chemiftry, may fome time or 
other attempt to analyze thefe bodies, and to fee 
whether they really are compofed of what may pro- 
perly be called falts, and of what kind. 
It is much to be lamented, that, in enquiries into 
the nature of foftils, there have not been more che- 
mical experiments made. 1 
VI. Experiments 
