434 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



American Institute Polytechnic Association, 



May 17, 1866. 

 Prof. Samuel D. Tillman in the chair; T. D. Stetson, Secretary. 



Balanced Steam Valye. 



Dr. Warren Eowell exhibited his balanced steam valve. It was 

 made to be placed on the steam pipe, and there act as a cut-off. 

 But it was found that cutting-off there does not possess any advan- 

 tage, so this is not of much practical use, but it is here shown as a 

 true balanced valve; as at a pressure of 100 pounds a finger can 

 move it, being balanced in all directions. 



Prof. li. P. Stevens then took the floor, and spoke as follows 



On Denudation and Transportation in Surface Geology. 



When one passes the disturbed portion of the Atlantic slope^ 

 crossing the mountains, and traversing the valleys, and reaches 

 the undisturbed portion of the interior of the continent, and there 

 finds valleys fronted by moderate hills, having in general smooth 

 and rounded outlines, he is naturally led to compare the one with 

 the other — -to note their points of difference, or unison — to mark 

 their phenomena, and inquire if the laws of disturbance are suiS- 

 cient to explain the phenomena, of the one, and not of the other, 

 and if so what other agency must one call to his aid, to relieve the 

 difiiculty ? 



H. D. Rogers, and his disciple J. P. Lesly, have written very 

 learnedly upon the valleys of the Appalachian system, or the dis- 

 turbed portion, and have called to their aid, upthrows and down- 

 throws, faults, fractures, synclinals and anticlinals, and all the 

 mathematical nomenclature, pertaining to phenomena, which are 

 liable to have the rigid laws of this science applied rigidly to 

 them. But these fail west of the mountains; we cannot lean upon 

 them; they serve us not. 



The most prominent topographico-geological feature of the inte- 

 rior, is that of our great lakes. Are they valleys of subsidence, or 

 denudations ? They are all of them very deep, save St. Clair and 

 Erie, three of them descend to, and beneath the level of the sea. 

 Associated with these valleys are those of New York State, lying 

 meridionally to the axis of Ontario. Some of these valleys are 

 partly filled with water, and partly with drift and alluvium, as 

 Geneseo and Cayuga ; others, as Otisco, have bold shores, with- 

 out alluvium, or drift ; others, as the Genesee, Irondequoit and 

 Conewango, are filled with earth material, and have only insignifi- 

 cant streams winding through them. 



