758 Account of certain Agate Splinters. [No. 166. 



6. As we believe the trap to be less ancient than the granite be- 

 neath it, so we naturally conclude the clay stratum to be less an- 

 cient than the trap upon which it rests, and which otherwise must 

 have submerged it. The agate pebbles seem evidently to belong to 

 the trap formation, in the solid substance of which they prevail in 

 such numbers as occasionally to give it the appearance of pudding 

 stone. The convulsion which shattered the agates under considera- 

 tion must have happened after the deposit of the trap strata, but I 

 think previous to the deposit of the clay bed, the first soil sprinkled 

 over the rocky surface. Whilst the valley was still a basin of naked 

 trap, the fall or rolling together of rocks might shatter even the solid 

 substance of agate. But this effect could be produced under water, 

 only I think at the foot of water-falls. And, that every agate of a 

 stratum, twenty feet in depth and many miles in area, should have 

 been subjected to this action, seems improbable. The very clay itself 

 belongs not to the formation upon which it rests ; but has been wafted 

 hither from mountains probably hundreds of miles distant, and thus 

 mixed up with the agates, by some deluge of a very extensive cha- 

 racter. And the appearance of these splinters of agate might lead 

 conjecture to regard the primitive soils of our earth, as ground from 

 the living rock, rather by some brief but most violent convulsion of 

 the elements, than by the gradual and equable action of an ocean, 

 in a succession of ages. 



7- With such speculations all Geologists are familiar; yet every 



fresh illustration seems worthy of attention ; and it is perhaps seldom 



that we have so clear an evidence of the action of secondary forces 



in an interval so remote as that separating the formation of the trap 



layers from the era of the clay deposit. 



J. Abbott. 

 4, Ballard's Buildings, 1st Sept. 1845. 



