iv APPENDIX. 



which they were probably formed. In such circumstances, I judge it best to 

 give the names according to the lithological characters, in which all agree 

 (ex. gr. gneiss, mica slate, talcose slate, argillaceous slate, hornblende slate, 

 limestone, &c.), and in the heading of each rock indicate, so far as we know» 

 from what fossiliferous rock it was derived. In some cases we feel quite con- 

 fident what that rock was. For Instance, coal plants have recently been 

 found in the deposits extending north-easterly from Worcester down the Mer- 

 rimack, marked on the Geological Map of the State and in the Catalogue as 

 argillaceous and mica slate. The rock near Boston in which trilobites have 

 been found is put into the Silurian and Cambrian formation. We are con- 

 vinced that the limestones of Berkshire county belong to the older Silurian 

 series, and not Improbably all the other beds of this rock in the State have 

 the same age, except perhaps that in Bernardston, which is probably as high 

 in the series as the Devonian. But we have thought it best to leave all the 

 limestones together, hoping that some organic relics may reward future 

 researches. It seems now, also, to be proved that the Quartz Rock of Berk- 

 shire county is metamorphosed Potsdam Sandstone, containing, as it does in 

 Vermont, the LInguIa and Scolithus. But perhaps the quartz from other 

 localities may not be of the same age, and, therefore, we leave all the quar- 

 troze aggregates together under their lithological name. 



Perhaps it ought to be added that the term Mctamorphie, as here used, Is 

 limited to the changes which fossiliferous and not hypozoic rocks have under- 

 gone. 



