[ 446 ] . 
The natural hiflory of thefe chryfofites, fo far as 
Mr. Da Cofla has been able to coiled it, is, “ that 
<c they were given him by the name of Brazilian 
“ emeralds, that they are a kind of cryflals fhooting 
“ into columns of no regular Tides or angles, but 
« canaliculated, or floated lengthwife. That as they 
« are all fragments, he fufpeds, they do not fhoot 
« in vacuities of flones, or fiffures of rocks, like 
“ other cryflals j but lie always clofely imbedded in 
i( the hard rocks (quartz) and are w allied from their 
tc laid beds by the torrents, in like manner as the 
<c Brazil and Guinea gold is ; which is the reafon of 
“ their being in fuch fragments.” He adds, “ that 
«« the cryflals, black, analogous to thefe, and im- 
« bedded in quartz, or hard rocks, are found in our 
« mines in Cornwall, and in other parts of Europe ; 
« fpecimens of fuch are in the Britifh mufeum, and 
< f in other cabinets. The Swedes call thefe bodies 
tc lapides cornei cryflallifati, and Wallerius has a 
< c corneus cryflallifatus viridis, which likely is this 
< c kind. The miners of Germany vulgarly call them 
“ Schirl, and fometimes our Englifh miners name 
“ them Cockle and Call. The ranging of this cryflal, 
« Mr. Da Cofla fays, as a lapis corneus, is not only 
* c erroneous, but ridiculous ; js it is truly a kind of 
« cryflal, and might with propriety be fynonymed 
« Cryflallus viridis columnaris lateribus inordinatis.” 
I fliall conclude this paper with a pailage in the 
Optics of Sir Ifaac Newton, which is one inflance, 
among many of the wonderful fagacity of that great 
man ; as it correfponds very well with what we now 
underlland of the eledtric fluid, which, by the con- 
tinual motion of its parts, is fo principally concerned 
