HORNBLENDE SCHIST. 305 



Stones belonging to the trap family. The prisms, 

 in these examples, are of similar general forms 

 and dimensions to those that occur in many mem- 

 ber^ of that extensive family ; and, when the 

 beds are horizontal and uppermost with respect 

 to the surface, as they are always at right-angles 

 to these, such rocks are not distinguishable from 

 overlying masses of trap, without a careful in- 

 vestigation of their geological character and con- 

 nexions. 



With respect to minuter varieties of structure, 

 or texture, it is only necessary to say, that, in- 

 dependently of the larger flexures and contor- 

 tions to which the laminar varieties are subject^ 

 in common with the gneiss with which they are 

 so often associated, they frequently present a mi- 

 nutely undulated disposition similar to that of 

 micaceous and chlorite schists. 



Both the magnitude and disposition of the 

 separate minerals which constitute hornblende 

 schist, are subject to great variation ; and hence 

 arise numerous varieties of texture, of which 

 the minuter details must be referred to the synop- 

 tic catalogue. The leading distinctions of tex- 



x 



