( 17 ) 
N°. VI. 
An Account of an ‘Earthy Subftance found near the Falls of 
Niagara and vulgarly called the Spray of the Falls : 
together with Jome remarks on the Falls. By RoBERT 
M‘CausLin, M. D. Communicated by BENJAMIN SMITH 
BARTON, M. D. 
& 
Read O@. HIS fubftance is found, in great plenty, every 
XA BAAD: where about the bottom of the Falls; fometimes 
lying loofeamongft the ftones on the beach, and fometimes 
adhering to the rocks, or appearing between the layers up- 
on breaking them. ‘The maffes are of various fizes and 
fhapes, but feldom exceed the bulk of a man’s hand. 
Sometimes they are of a foft confiftence and crumble like 
damp fugar; whilft other pieces are found quite hard, and 
of a fhining foliated appearance; or elfe opaque and re= 
fembling a piece of burnt allum. It often happens that 
both thefe forms are foundin the fame mafs. Pieces which 
are taken up whilft foft foon become hard by keeping ; 
and they are never known tocontinue long in a foft ftate, 
as far as I have been able tolearn. In order to determine 
the nature of this fubftance, I made thefollowing experi- 
ments. 
Exp. tf. I put an opaque piece, weighing 14 grains, 
into the vitriolic acid diluted with three times its quantity 
of water; And letitremain there twenty-four hours, fhak- 
ing it now and then. Not the leaft effervefcence enfued, 
and on taking out the piece it weighed near one grain more 
than when it was putin, although care was taken to ab- 
forb the moifture which was upon its furface. This ex- 
periment was repeated with a fhining piece, and with ex- 
adtly the fame refult. 
Exp. 2d. When put into vinegar it did not produce the 
leaft effervefcence. The vinegar having ftood upon it fome- 
VOL. IL. C time 
