56 Geology J ^c. of the Cormecliciit. 



very considerable is the quantity of rock yearly detached, 

 and compare this with the whole amount of the debris, the 

 conclusion forces itself upon us that the period when this 

 process began could not have been vastly remote ; in oth- 

 er words, that the earth has not existed in its present form 

 from eternity. Its precise age cannot, indeed, be deter- 

 mined by this chronometer ; but I have often thought that, 

 judging from this alone, we should be led to conclude that 

 Moses placed the date of the creation too far back, rather 

 than not far enough. 



Greenstone Dykes in Old Red Sandstone. 



Professor Silliman conducted me to an interesting locali- 

 ty of these in East-Haven. They occur on the main road 

 from New- Haven to East Haven, less than half a mile from 

 Tomlinson's bridge. We measured their width, and that 

 of the intervening sandstone, as they appear on the north- 

 easterly side of the road. The road here passes over a 

 small eminence, and the bank, on the north side, in its high- 

 est part, is almost fifteen or twenty feet above the road. 

 The dykes, occurring at this place, are exhibited on the pro- 

 file accompanying the map; and are laid down from a scale 

 of fifty feet to an inch, with the intervening sandstone. In 

 describing them 1 shall begin at the north western extremity, 

 that is, at the point nearest New-Haven: but a person wish- 

 ing to find them, will do best to go first to the other end of 

 the profile ; because the dikes are there more distinct. 



No. 1. (See Profile.) Old red sandstone, coarse and con- 

 taining pebbles so as to form a conglomerate. The dii> of 

 the strata is from 6° to 10° below the eastern horizon. The 

 sandstone is very similar throughout. 



No, 2. Greenstone dike, 4 feet thick. 



No, 3. Sandstone, H 4 feet. This distance was measur- 

 ed by pacing ; the other distance by a rule. 



No. 4. Greenstone, one foot thick. 



No. 5. Sandstone, 9 feet. 



No. 6. Greenstone, 9 feet. 



No. 7. Sandstone, 40 feet. 



No. 8. Greenstone, 1 teet. The soil has so covered this 

 spot, and we having nothina: with which to penetrate it. we 

 did not actually see the dike. But the walls are distinct, 



