Ill. Account of a SeriEs of EXPERIMENTS, /hewing the Er- 
FECTS of CoMPRESSION in modifying the ACTION of HEzEatT. 
By Sir JAMES HALL, Bart. F.R.S, Evin. 
" [Read Fune 3. 1805.] 
I. 
Ancient Revolutions of the Mineral Kingdom.—Vain attempts to explain 
them.— Dependence of Geology on Chemiftry.—Importance of the Carbo- 
nate of Lime—Dr Buacx’s difcovery of Garbonic Acid, fubverted the 
former theories depending on Fire, but gave birth to that of Dr Hor- 
ron.—Progrefs of the Author’s Ideas with regard to that Theory. 
—Experiments with Heat and Compreffion, fuggefted to Dr Hurron 
in 1790.—Undertaken by the Author in 1798.—Speculations on which ~ 
bis hopes of fuccefs were founded. 
HOEVER has attended to the ftruéture of Rocks. and 
Mountains, muft be convinced, that our Globe has. not 
always exifted in its, prefent ftate ; but that every part, of its 
mafs, fo far at leaft as our obfervations reach, has been agitated 
_ and fubverted by. the moft violent reyolutions. 
Facts. leading to. fuch ftriking conclufions, however i imper= 
feétly obferved, could hot fail. to, awaken. curiofity, and give rife 
rit 
to. a defire of tracing, the, hiftory, and) of inveftigating the 
made in this way, but with little fuccefs ; for while difcoveries 
of 
