34 Mr. W. J. Hamilton and Mr. H. E. Strickland, on the Geology of 



It is evident from the phsenomena here exhibited, that however recent may be 

 the appearance of the lava-stream, and of the cone from which it flowed, a very 

 high antiquity must in reaUty be assigned to them. It is certain, from historical 

 testimony, that no volcanic eruption has taken place in this country for at least 

 thirty centuries, and how many more may have been required to enable the Her- 

 mus to denude the solid lava to the extent we now see, it is not easy to calculate. 

 It would not indeed be fair to assume, that the whole of the present channel of the 

 river between the lava and the mica-schist has been excavated to the depth of 

 eighty feet since the flowing of the lava ; for the rounded margin of a coulee com- 

 monly leaves a hollow between it and the pre-existing rock, which the river would 

 naturally follow, and by undermining the columnar lava might produce a perpen- 

 dicular chfl" in less time than would at first sight be supposed. But when we find 

 the river cutting across the couUe, and passing from one side of the lava to the 

 other, we can assign no other satisfactory cause for this phaenomenon than the me- 

 chanical action of the river, operating during vast periods of time, and gradually 

 wearing down its bed to its present level*. 



The freshness of appearance in the three great cones, the vast antiquity of which we 

 have thus demonstrated, proves how small is the effect of atmospheric agency upon 

 volcanic products, when unassisted by running water. Had these volcanos been 

 ejected within the last ten years, the cones of scoriae could hardly have been more 

 perfect, the craters better defined, or the streams of lava more black, rugged and 

 barren. Nor is this difficult to explain, when we remember, that the lava and scoriae 

 in this region seem to have scarcely any tendency to chemical decomposition, and 

 that the rain which falls on the cones, being instantly absorbed by their porous soil, 

 exerts no other mechanical force than the mere impact of the drops in falling. 



These considerations render it difficult to explain the marked difference of appear- 

 ance between the volcanic products of the second and of the third periods, on the 

 mere assumption of a difference in their ages. It appears to us that a tenfold 

 greater period of time, than has already elapsed since the ejection of the volcanos of 

 the third period, would barely suffice to reduce them by atmospheric agency alone 

 to the smooth and rounded forms presented by the cones of the second period; but 



* The above observations, respecting the agency of running water in cutting through the lava-stream, 

 are Mr. Strickland's. In justice to himself, Mr. Hamilton is obliged to state that he does not agree with 

 the opinion, that the cutting across the coulee and the formation of the cliff are at all owing to the eifect 

 of running water acting upon the adamantine basalt. The very circumstance of the perpendicularity of 

 the sides is an argument against it. He is rather inclined to attribute it to the fall of the basaltic masses 

 in consequence of their having been undermined by tlie waters, the operation of which cause may have 

 been hastened by fissures and crevices produced by the numerous earthquakes to which this country has 

 at all times been exposed. — W. J. H. 



