424 APPENDIX. 



vious to his departure for Europe, showed me 

 tiful specimen of obsidian, belonging to his Mineralogi- 

 cal cabinet, with a complete Echinite imbedded in it; 

 this specimen is in a state of conservata, and not calcin- 

 ed. This is a curious fact, as it offers an objection to a 

 generally received opinion, that obsidian is of volcanic 

 origin ; and if it was so, the calcarious matter must have 

 been decomposed. 



I would also make another observation with respect 

 to an opinion of Cuvier. He says that crystallized mar- 

 bles never cover shelly strata. Perhaps this may be the 

 case in that part of Europe which has been examined 

 by him ; but I have discovered granular foliated lime- 

 stone, perfectly crystallized, in the County of Columbia, 

 in the neighbourhood of Hudson, containing pectinites, 

 anomites, terebratulites, &c. specimens of which I have. 



There have been some inquiries made with respect to 

 the rocks catled the Pallisadoes, opposite Mount Pleasant, 

 on the Hudson river. On examination, I found the lower 

 stratum running under the river, composed of a beauti- 

 ful red granite, and the superincumbent matter consisting 

 of a species of basalt, of the trap family. This mass of 

 rock takes a westerly and northwesterly direction towards 

 the falls of Passaick, and there becomes the trap of the se- 

 condary formation; in which I found several pieces of 

 agate, imbedded in a similar manner to some specimens I 

 have received from Leo. M'Nally, Esq. of Dublin, which 

 ke obtained near the Giant's Causeway. 



