[ 59 ] 
I was firft led to entertain thefe thoughts, byob- 
ferving the nature of Briftol dones, and the various 
dates in which they appear j and was encouraged to 
think they might have fome little weight, by ob- 
ferving alfo the nature- of fpars, and of thofe flony 
concretions found in large caverns. I (hall, there- 
fore, firft mention the obfervations I made, 'and then 
draw my conclufibns. 
1. And lii the , finT place, it is known, that 
'the Briftol flones grow, within the hollow cavity 
of fome other rough rfone| and that the fubdance 
of the external done is porous, and frequently fo 
1 drongly impregnated with crystalline corpufcles, that 
they glitter amongd die earth}; particles, when held 
up to the light: • 
2. In the next place, it is to be obferved, that, 
wherever there is a.' hollow cavity in thefe kind of 
dones, the infide is almod always lined with fuch 
fhining fubdances, • either in a perfect or imperfeft: 
date. . . 
3 . We find the Br idol dones appear in feveral dif- 
ferent dates : i for in fome places of the cavity, where 
the crydaljization is not completed, they are of- a 
dufky red, without any tranfparency ; in others they 
appear of a dirty yellow j and in others white ; and 
.-at lad tfanfparent. 
'4. As to the ' fpars and cry dais formed even in 
-dints, and other- hard bodies 5 I think they are gene- 
, rally obferved in fuch as have evidently been at one 
time or other in a 'loft date, and lay in or near mold 
places drongly, impregnated with Inline paiticies o- 
fdme kind or other. ; or elfe they, are found in bodies 
wherein fome falirie and mold fubdances 'have foi- 
■ I 2 merly 
