t ] 
oi* upwards. He told me, he believed the Stone had 
been growing there for near thirty Years j but never 
apprehended it to be a Stone, but tjfed to complain 
of a Weight, as if it were half a Pound, carried be- 
tween his Legs. 
^ohn SiJlejif 
Surgeon and Apothecary, 
Town- Mailing, Kent* 
XVn. A Letter from Mr. Moreton Gilks, 
F. R. S. to Dr. Mortimer, Sec. R. S. giving 
feme Account of the Petrefacflions near Mat- 
lock Baths in Derbyfhire 5 with his Con^ 
je6iures concerning D etrefaTiion in General. 
SIR, 
I N the mountainous Part of Derbyfhire, about 
Cromford, is a Valley of at leaft a Mile and half 
long, walled on each Side with high craggy Rocks j 
theEaft Side cliffy, the Weft more reclining, but ex- 
tremely rough and difficult of Afcent ; being com- 
pofed of large loofe Pieces of the Lime-ftone Rock, 
of five, ten, or twenty Ton Weight? that feem at 
fome Diftance of Time to have broken off from the Top 
of the Cliffs, and fallen down into the Valleys. 
At the Bottom of the Valley, which feems to be a 
great gaping Fiffure of the Rock, runs the River 
Derwent harfhly along its rocky Bottom. About 
the Middle of the Valley, at near 50 Foot perpen- 
dicular Height from the River, iffue forth feveral 
Ri- 
