had been imbedded, and with the particles of which it had been 

 pervaded for several thousand years. 



Rosinus, having remarked the separation of several laminae front 

 fossil shells, each preserving the regular form of the shell : and having 

 also observed in several circular asteriae, which had undergone a con- 

 siderable degree of decomposition, that one layer separated after an- 

 other; and that, although the size of the stone became thus dimi- 

 nished, the figure, which it had before possessed, was still preserved, 

 he was led more closely to examine into their internal structure. For 

 this purpose he rubbed down several asteriae on a proper stone, and 

 found, that although he thus reduced their size, yet the same figure 

 which had adorned their surfaces was still discoverable, when the new 

 surface was brought up to a polish. This circumstance, though most 

 easily demonstrated, in pentaphylloid asteriae, is, he observes, al- 

 though not so constantly, nor so easily, also demonstrable in the other 

 asteriae. 



From this circumstance he infers, that the increase of these bodies 

 must have taken place, by the regular apposition of new matter on 

 the original figured surface ; and that hence the original figure is found 

 to pervade through the whole substance *. M. Walch, however, con- 

 tends that Rosinus is here mistaken, and asserts, that the markings on 

 the horizontal surfaces of these bodies are but superficial, and should 

 be considered as so many apophyses f. 



To enable me to form a just opinion on this point, I rubbed down 

 several trochites and asteriae ; and was thereby satisfied, that neither 

 the star nor the flower passes through the whole substance, but, on 

 the contrary, that, in by far the greatest part, they are not discover^ 

 able at all beyond the surface. Jn that species of asteriae, whose cir- 

 cumference is nearly circular ; and this species Rosinus describes as ex- 



* De Lithozois, p. 9. 

 f Recueil des Monumens des Catastrophes, &c. Tom. II. p.67. 



