GEOLOGY. 283 



North Carolina. Here then, in all respects, is the culminating region 

 of the vast Appalachian system. 



Professor Guyot also notices at length the remarkable depression in 

 the Appalachian system between the northern and middle divisions, 

 above referred to, which attains its lowest point in New Jersey, in 

 the parallel of New York city. This depression causes the continen- 

 tal plains which form the natural base of the mountain system to 

 disappear at this point under the waters of the ocean. The waters 

 of the tide thus come to bathe the very base of the mountains, and 

 the region of plains fades away on the frontiers of New Jersey and 

 New York, while towards the south the plains at the base of the 

 mountains gradually enlarge, and in North Carolina reach a breadth 

 of over two hundred miles. 



This depression seems to be due to a local subsiel^nce of the earth's 

 crust at an epoch undetermined, it is true, but which must have been 

 posterior to the principal upheaval of the Appalachian Mountains. 

 A fact, the discovery of which is due to the sagacity of Prof. J. D. 

 Dana, seems to give weight to this opinion. He demonstrated by 

 means of numerous soundings, marked upon the excellent marine chart 

 published by the United States Coast Survey, the existence of an 

 ancient channel, a continuation of that of the Hudson River, which 

 goes out from the Bay of New York through the Narrows, and ad- 

 vances far out under the waters of the ocean. It is not possible to 

 suppose that such a channel, which is constantly liable to be obliter- 

 ated by sand-banks formed by the motion of the sea, could have ever 

 been formed in its present position. In order that the current of the 

 river should excavate this channel it is necessary to suppose that the 

 bottom of the sea has once occupied a higher level, above or very 

 near the surface of the ocean. The shallowness of the ocean for a 

 considerable distance from the coast of New Jersey also indicates a 

 prolongation of the continental plains under the sea, and the limit of 

 the deep waters is there found at a distance nearly double that which 

 is observed off the coast of the Carolinas. Moreover, the parallelism 

 which exists between the line of coasts and all the great general in- 

 flections of the Appalachian system, a parallelism which is well 

 marked from Nova Scotia to Florida, here undergoes a modification 

 which is well explained only by a local depression of this part of the 

 system. The fact that all New Jersey is now undergoing gradual 

 submergence from Cape May to the Bay of New York, which is 

 proved by numerous facts gathered in the Geological Survey of the 

 State of New Jersey, is here not without signification. 



NOTES ON THE H^TORT OF PETROLEUM, OR ROCK OIL. 



In the Canadian Naturalist (July, 1861), Mr. T. Sterry Hunt, 

 F. R. S., of the Canadian Geological Survey, gives the following com- 

 prehensive resume of the most important facts thus far made known 

 respecting the geological history of the various substances designated 

 as " petroleum," "rock oil," " naphtha," " asphalt," " mineral pitch," 

 etc. All of these, says Mr. Hunt, are forms of bitumen, some of 

 which are solid, and others fluid, at ordinary temperatures ; the more 

 liquid being mixtures of oils differing in volatility, which by exposure 



