46 Dr. Berger o?t the Isle of Man, 



II. Compound Rocks 7iot hi Situ, 



(^) Primitive Rocks, 



Granite. 

 I am aware but of two modes of explaining the existence of loose 

 blocks of rocks that are spread over the face of a country, what- 

 ever may be the nature of the blocks themselves, either to suppose 

 they are extraneous to the places where they now lie, or that, howsoever 

 unconnected they may appear to be with the materials that surround 

 them, they are nevertheless in their birth-place, and have been dis- 

 integrated in situ, covering and resting upon solid and continuous 

 strata similar to themselves. 



The only criterion perhaps applicable to the determination of 

 this important question is the following. When by farther inves- 

 tigations we have found that the hidden and continuous rocks are 

 similar to the blocks themselves, we may safely venture to say that 

 the latter are indigenous. 



I am inclined to think that several of the loose blocks I am going 

 to describe, whenever they occur in anj number, are in their birth- 

 places. 



On the beach towards Aire-point there are innumerable loose 

 blocks of granite, one of which, rather large in its dimensions, I ob- 

 served on Aire head at the elevation of 271 feet. They all in their 

 characters differ but little the one from the other. The rock is a 

 small-grained granite, composed of white felspar, quartz and black 

 mica, with a few incidental plates of the latter that are white. In 

 one of the specimens I collected, there is a rectangular piece one 

 inch in length by half an inch broad, of very minutely grained 

 granite with a predominance of mica. 



