[ 24 6 ] 
with beds of oker, and the waters are fometime? 
much tinged with it. 
» 4thly, The cavity left in the middle of the block 
js not perfectly fimilar to the original cavity of the 
trunk, or pipe 3 becaufe the water did not flow quite 
uniformly over the edges, at the ends of the {hoots 
or troughs, in confequence, probably, of their not 
lying exactly horizontally : whence, more water 
fell upon and againfl: one part of the fldes of the 
trunk, than againfl; the other. 
5thly, The outfide of the block has taken off im- 
preflions of all the roughnefles, knots, and fliivers of 
the elm boards, which compofed the trunk or pipe, 
even more accurately than they could have been 
taken off by wax, plaifter of Paris, or almofl: any 
compofition whatever, and certainly much more 
durably which impreflions, although they are not 
fo well reprefented in the drawing, in confequence 
©f their ffnenefs, yet appear fufficiently plain, both 
on the fpecimen here defcribed, and on that prefented 
to the Society, and are exceedingly well deferving. 
of notice. 
There is in the PhilofophicalTranfactions (Vol.LX.. 
p„ 47.) a very curious paper, from our learned foreign 
Member R. E. Rafpe, concerning the production of 
white marble in a fimilar manner ; in which paper 
he mentions the taking off impreflions of medallions, 
by means of petrifying waters. And I remember a 
paper was read at the Royal Society fome time ago, 
containing an account of feveral impreflions, actually 
lo taken off in a fhort time, in durable marble, by 
means of a petrifying water, near Bologna in Italy: 
when fome of the impreflions were alfo lent, both to 
the. 
3 ; 
