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EXAMINATION of the SUPPOSED IGNEOUS ORIGIN 

 of STONY SUBSTANCES. By RICHARD KIRWAN, 

 Efq; F. R. S. and M. R I. A. 



JL HE origin of ftony fubftances, feemlngly an objedt of mere Read Feb. 

 curiofity, is neverthelefs connecfled with deliderata of the greateft 3> 1793- 

 utility to mankind; to fay nothing of the arts of fabricating 

 glafs, artificial gems, mortal', cement, bricks, pouzzolane and 

 earthen- ware, which have evidently fome reference thereto, 

 nature prefents us with various ftones, as flates, mica, &c. with 

 whofe artificial compofition, though highly important, we are 

 at prefent unacquainted, and mufl remain fo until the mode 

 of their produdtion is fatisfadorily afcertained ; then, and then 

 only, experiments tending to form them by art may be planned 

 and attempted. Hence the propriety of examining the foun- 

 dation of the different opinions of mineralogifts and geologifts on 

 this head ; if we can exclude any of them, we are fo much the 



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