GEOLOGY. 359 



feet; 8. Sogar-Loaf (or Hallback Peak), 6,401 feet; 9. Potatoe Top, 6,389 

 feet; 10. Black Knob, 6,377 feet; 11, Bowler's Pyramid, 6,345 feet; 12. 

 Roan Mountain, 6,318 feet. 



THE HORIZONTAL HEAVE OF ROCKS. 



At a recent meeting of the Boston Society of Natural History, Prof. Wm. 

 B. Rogers made some remarks upon a peculiar geological condition which 

 he had noticed in the Slate Rocks of Governor's Island in Boston harbor, 

 and of which he had never seen any notice. At the landing near the fort, 

 where the slate is exposed, he had observed a series of ledges of dark gray- 

 ish-blue slate, in which is exposed a species of fault known as horizontal 

 heave. There are two lines of direction in the beds, and these are at right 

 angles with each other. This phenomenon of horizontal heave, combined 

 with the system of cross cleavage which is at right angles with the planes 

 of bedding, creates some obscurity in some spots as to which are the original 

 planes of bedding. In ot'icr localities, especially in the Quincy and Brain- 

 tree silicious slate in which trilobites have been recentlv found, the same dif- 



* 



faculty exists ; rendering it impracticable to obtain perfect specimens of that 

 fossil in any amount, since the rock splits off in an opposite direction to that 

 in which the animal was deposited. 



This system of horizontal heave has been extensively studied in Europe, 

 and has elicited much discussion from geologists and physicists upon the 

 theory of the phenomena engaged in its production. It is supposed that a 

 great pressure has been applied to the rocky mass, either before or after it 

 had reached a complete state of solidity, and that this pressure has produced 

 such a structural arrangement as to develop particular planes of cleavage 

 where the adhesion was the slightest. This supposition has been sustained 

 by experiment, recently instituted in England, in which it has been demon- 

 strated that scales of mica and other material of flattened form, intermingled 

 with plastic clay and submitted to continuous and energetic pressure, assume 

 approximate parallelism, and impai't to the mass a laminar structure. 

 AYhcre cleavage shows itself in limestone containing mica scales and flat- 

 tened particles of silica, the microscope has detected an approximate degree 

 of parallelism between these substances and the cleavage planes. 



OX THE LAKES OF EASTERN ASIA. 



At a recent meeting of the London Geological Society, Mr. Loftus read a 

 paper on "An Analysis of the Water in several of the great lakes at the 

 base of Mount Ararat, and the Mountain Chains of the Kurdistan between 

 Turkey and Persia." The water of Lake Vann and the others he described 

 as remarkable for containing immense quantities of salts, chiefly those of 

 soda, as the carbonate of soda, the sulphate of soda, together with chloride 

 of sodium (common salt). It was supposed that the springs which feed 

 these lakes dissolve large quantities of soda and potash out of the volcanic 

 rodks with which they came in contact and deposit these salts in the lakes. 

 As the water evaporates the strength of the solution increases, year by year, 



