C 243 ] 
are merely tranfverfe fedtions of the fubftance, with 
which the pipe was filled. 
The water, that flowed into the pit on all fides, 
iflued from a ftratum of hard brown and reddilh 
fand-ftone, replete with fhining fparry mica, and 
fome ocherous matter j and had, in its paftage 
through the trunk, regularly filled up the cavity, 
by flow degrees, with folid incruftations ; infomuch, 
that the increafe of the marble is marked much in 
the fame manner as the increafe of the growth of a 
tree appears to be, when the trunk of it is cut hori- 
zontally : and at laft the water had left only the ca- 
vity, which now appears in the middle of the block, 
and which was uniform in its figure from one end 
of the pipe to the other, and nearly fimilar to the 
original cavity ; but which, at laft, not being large 
enough to let all the water pals, occafioned the dis- 
covery. Since that time, in order to prevent the in- 
convenience (if poffible) a new trunk has been made, 
larger than the firft ; and yet, in June 1771, this 
new trunk alfo was fo far filled up with the fparry 
incruftation, that there was but juft room to thruft 
four fingers into the central cavity j and the lateral 
fhoots, or troughs, alfo have filled fo faft, that they 
have been obliged, every now and then, to clean 
them out. 
This, Sir, .is the hiftory of the fpecimen now laid 
before the Society, and of the Mine from whence it 
came j and the obfervations I would beg leave to 
make, are the following. 
1 ft, As the water flowed in from the fhoots, on 
two fides of the fquare trunk or pipe, it is manifeft 
that the ftreams muft have ftricken againft each. 
Vol. LXIIL K k other* 
