[ 2 45 ] 
2dly, At the place marked B, Fig. i, there Teems 
to have been, by Tome accident or other, the point 
of a fmall nail projecting into the pipe ; and here, it 
is very remarkable, that, either by the dafhing of the 
water, or rather perhaps by an effeCf which iron has 
been obferved to have of haflening and increaling 
petrification, the incruftation has gone on fatter 
than in other parts of the fame fide ; but fo regu- 
larly, that, from the point of the nail to the inner 
cavity, there is a fwelling, or protuberance, fo uni- 
form, that it makes throughout nearly the fame feg- 
ment of different circles, of which the point of the 
nail is the common center ; and that not merely 
direCtly oppofite to the nail, but throughout this 
whole block and even further downwards. 
^dly, The regular increafe of thefe fegments of 
circles is vifible in each lamina of the block (if I 
maybe allowed that expreffion), and in each lamina 
the diameter of the circle increafes in due proportion ; 
fo that it is ftill nearly the fame fegment ; though, 
if there be any difference, it is rather a fmaller por- 
tion of a larger circle ; as, from the caufe which 
occafioned it, one would be led to expeCt. And 
with regard to thefe lamina, it is worth obferving, 
that as they mark the increafe of the marble uniformly 
all round, as the growth of a tree is marked (only the 
marble increafed inward, whereas a tree grows out- 
ward) fo they feem to have become vifible, and to 
have been thus diftinCtly marked, by means of the 
water bringing, at different times, more or lefs oker 
along with the fparry matter : and this is the more 
probable, as the whole country all round abounds 
K k 2 with 
