o 



88 



ILLUSTRATIONS OF 



faltes, and which has acquired a high degree of 

 induration, by the vicinity of the great ignittd 

 mafs of whinftone. 



This folution of the difficulty has fince been 



firmed by obfervatio 



Dr Hop 



h 



de on the fpot by 



difcovered tvvo or three 



tions of the bal'altic rock, with the beds of the 

 fchiftus in which the fliclls are contained. 



obfervations of 



253 



This alfo explains fome 



Spallanzani, made in the ifland of ■' -erigo, on the 

 coaft of Greece, the Cytha^ra of the ancients*. 



The bafe of that ifland is iimeftone 



but it 



/ 



^ 



abounds alfo in unftratified rocks, which the 

 Italian naturalift fuppofes to be of volcanic ori- 



1 



gin ', but which, if I miftake not, we would re- 

 gard as whinftone, or perhaps porphyry ; and 

 they are faid to contain oyfterlhells and pec- 

 ten ites of a large fize, perfedly mineralized. 

 Thefe petrifadions, however, Spallanzani fays, 

 /are not contained in the lava that has ac- 

 tually flowed, but in ftones which have only 

 endured a fllghter acClion of fire. Without the 



I 



commentary afforded by the Portrufli fpecimens, 



it would be difficult to make out any thing very 



precife from this defcription. By help of the 



information derived from thofe fpecimens, we 



may conclude, that the condition of the fliells 



in 



I » 



* Journal de Phyli«jiie, torn, xlviii. (1798), p. 278 



