GEOLOGY. 255 



matter from below through the opened fissures. Fifthly. Earth- 

 quakes, or a vibration of the earth's crust, would be consequent on a 

 rupture, internal or external, and would cause vibrations of the sea, 

 besides other effects. Sixthly. These changes would make epochs in 

 geological history. Seventhly. The courses of mountains and coast 

 lines, and the general form of continents, were determined to a great 

 extent by the general direction of the earth's cleavage structure, and 

 the position of the large areas of the greatest contraction. 



ELEVATION OF AN ISLAND IN LAKE SUPERIOR. 



THE Lake Superior Journal states that, on June 18th, in the vicinity 

 of Two Heart River, a slight agitation of the water was perceived near 

 the shore, and soon a small round island, about 150 feet in circumfer- 

 ence, was raised six feet above the water. The new island was at first 

 covered with sand and pebbles, but the waves have dashed over it since, 

 and washed it down to a black clay. The immediate shore was at the 

 same time raised up about twelve feet, but a few rods back a circular 

 spot of ground suddenly sunk down twenty feet. No noise or agitation 

 of the earth was perceived. 



CONNECTION BETWEEN AMERICAN AND EUROPEAN GEOLOGICAL 



FORMATIONS. 



AT a meeting of the Boston Society of Natural History, in Febru- 

 ary, Prof. Wyman exhibited specimens of fossil teeth from the terti- 

 ary deposit of Richmond, Ya. They belonged to the genus Phyllodus, 

 and possessed an unusual form. Prof. Rogers said he considered 

 these specimens particularly interesting, as illustrating the fact that the 

 eocene and miocenetleposits of Europe are not parallel with, and equiv- 

 alent to, those of America. The genus Phyllodus occurs in the London 

 clay, eocene, while the Richmond deposit is considered miocene. The 

 eocene and miocene of Europe are more closely related to each other 

 than the layers of tertiary in America. Mr. Desor remarked that the 

 London clay had been regarded of late by some geologists as allied to 

 the miocene. He agreed with Prof. Rogers as to the want of a com- 

 plete correspondence between the American and European tertiary, and 

 also with regard to the absence of a close connection between the 

 American tertiary of different epochs. 



Mr. Desor also exhibited a shark's tooth from the limestone deposit 

 at Keokuck, Iowa, on the right bank of the Mississippi. It resembled 

 the teeth of the genus Psammodens. By comparing with the teeth of 

 the Port Jackson shark, which, however, are much smaller, an infer- 

 ence might be drawn as to the size of the species. The Port Jackson 

 shark being three or four feet in length, the size of this species must 

 have been very great. There was a doubt, Mr. Desor remarked, as to 

 the true geological position of the limestone from which this speci- 

 men was procured. The Western strata cannot be so readily referred 

 to those of Europe, as those of the eastern parts of the United States. 

 The distinctive traits of the strata of the East diminish on going west. 



