1824.] 



An Account of the Logan Rock. 



411 



The foundation of the whole is a stupendous group of granite 

 rocks, which rise in pyramidal clusters to a prodigious altitude, 

 and overhang the sea. On one of those pyramids is situated the 

 celebrated Logan Stone, which is an immense block of granite 

 weighing above 60 tons. The surface in contact with the under 

 rock is of very small extent, and the whole mass is so nicely 

 balanced, that, notwithstanding its magnitude, the strength of a 

 single man applied to its under edge is sufficient to change its 

 centre of gravity, and though at first in a degree scarcely percep- 

 tible, yet the repetition of such impulses, at each return of the 

 stone, produces at length a very sensible oscillation ! As soon as 

 the astonishment which this phenomenon excites has in some 

 measure subsided, the stranger anxiously inquires how, and 

 whence the stone originated — was it elevated by human means, 

 or was it produced by the agency of natural causes? — Those who 

 are in the habit of viewing mountain masses with geological 

 eyes, will readily discover that the only chisel ever employed 

 has been the tooth of time — the only artist engaged, the ele- 

 ments. Granite usually disintegrates into rhomboidal and 

 tabular masses, which by the farther operation of air and moist- 

 ure gradually lose their solid angles, and approach the spheroidal 

 form. De Luc observed in the Giant mountains of Silesia, 

 spheroids of this description so piled upon each other as to 

 resemble Dutch cheeses ; and appearances, no less illustrative 

 of the phenomenon, may be seen from the signal station to 

 which we have just alluded. The fact of the upper part of the 

 cliff being more exposed to atmospheric agency, than the parts 

 beneath, will sufficiently explain why these rounded masses so 

 frequently rest on blocks which still preserve the tabular form ; 



