434 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



until the shot is near the muzzle. Quick burning makes no more heat or 

 power, pound for pound, but applies it to more advantage by acting with 

 greater force at the beginning, and the same near the muzzle, as slow pow- 

 der, if the guns will bear the strain. He (Mr. W.) proposed guns that 

 should endure this strain and consequently would allow of the advantage- 

 ous use of quick powder. 



Mr. Dibben explained on the blackboard that the muzzles of guns received 

 more heat than the breech, and therefore the metal at that part should 

 become hot before the latter from another cause than its reduced thickness. 

 He thought, on motion of the gases at their release, by presenting fresh 

 particles of the heated gas to the surfaces, more rapidly than at the breech, 

 where it was relatively stagnant, allowed the metal to receive, near the 

 muzzle, more actual increments of heat. 



The subject was continued. 



Adjourned. Thomas D. Stetson, Secretary. 



American Institute Polytechnic Association, ) 

 January 2, 1863. ) 



The Chairman, S. D. Tillman, Esq., presiding. 



Mr. J. H. Churchill read a paper on the artificial formation of saltpeter. 



Dr. R. P. Stevens made some remarks on the newly discovered lead mines 

 in the Shawangunk grits, Orange county, N. Y. 



The history of the mine is briefly this: In grading for the New York and 

 Erie railroad down the slope of the Shawangunk mountain, , from the sum- 

 niit at Otisville to the level of the Delaware river, at Port Jervis, nearly 

 midway of this descent, and opposite the village of Cuddebackville, in the 

 Neversink valley, the workmen made discoveries of boulder lead, or masses 

 of lead ore lying in the earth covering the slope of the mountain. Though 

 the specimens were rich and wonderful, they excited little more attention 

 than to amuse the curious. Some years later, in building a mountain road, 

 the Messrs. Guamaers found other and richer specimens. Some of these 

 were brought to this city and exhibited to mineral men. This exhibition 

 led to an examination of the locality, which speedily resulted in the dis- 

 covery of the richest lead mine yet opened in the whole range of these 

 mountains, extending as they do from Tennessee to the North river. 

 r You will better understand the peculiar features of this mine, after I 

 shall give a brief geological description of the Shawangunk mountains. 



These mountains stretch across the southeastern corner of our State, 

 from near Rondout, to the New Jersey line, at Port Jervis, in a S. S. W. 

 direction. The following great geological formations compose their bulk, 

 first- on the east, and forming the main mass of the mountains, lie dark brown 

 and blackish colored slates, which we should call the Taconic slates of Dr. 

 Emmons, known in our State geological report as the Hudson river group. 

 They are from 3,000 to 5,000 feet in thickness, and, with other members of the 

 group, fill up all the country along the Hudson river from Newburgh to 

 the mouth of the Rondout creek. This slate rock is destitute of minerals. 



