[ «9i ] 



are found equally announced on each of the oppofite fides, with 

 this difference however, that more or lefs of the prominent 

 brown matter of the bones, fins, and other parts, fometimes 

 adheres to one leaf and fometimes to another, or frequently 

 is divided between both ; the prominences on one fide, when 

 the pieces have been carefully and well put together, being ex- 

 a£lly anfwered by correfponding hollows on the other ; and thus 

 the more valuable fpecimens are formed in duplicates. This, 

 properly confidered, muft furely make the difficulty of fabrication, 

 in fuch inftances at leaft, fo great, that it may well be deemed 

 infurmountable ; and if not from the nature of the cafe itfelf, 

 yet decidedly fo at fuch an expenfe, as either the capita! of the 

 late proprietor, or the prices at which I underftood he fome- 

 times parted with fpecimens, would bear ; fome in his, as well 

 as in Marquis Gazola's own cabinet, were of an immcnfe fize ; 

 certainly, as the catalogue mentions, fully three feet long. " 



I HAVE now related all the fads worthy of notice which I 

 recoiled; to have fallen within my obfervation relative to thefc 

 curious foffils ; and I truft I have done fo faithfully and with- 

 out a view to any particular theory or fyftem of explanation : 

 In fad, I vifited the fpot where they are found wholly unpre- 

 judiced as to the manner of accounting for the pha?nomenon, 

 and indeed wholly uninformed, as I ftill am, of any attempt to 

 account for it, except on vague and general principles *. What 



O o 2 I fhall 



* Whether the following attempt to affign immediate caufes for the produftion 

 of the phsenomena now defcribed can lay claim even to noveliy, as a recomrnenda- 



tion 



