482 



TRANSACTIONS OF THE AMERICAN INSTITUTE. 



A, tho point at which 



The subject selected f 

 Adjourned. 



the steam is cut off; B, the pressure at the end of 

 the stroke; the dotted lines show the 

 hyperbolic curve; the lightly shaded 

 squares the amount to be deducted 

 when the steam is used at full 

 pressure; the heavy shaded squares 

 the force that is to be deducted after 

 the steam is cut off; the very light 

 shaded squares within A, B, C, 

 represent the diminished eifect 

 when cutting- off at one-quarter of 

 the stroke. 



The Chairman said there was a 

 latent force in the steam unex- 

 panded, which it appears is lost if 

 the steam is allowed to follow the 

 piston through its whole length as 

 if it were a solid plug. How we 

 could best take advantage of the 

 expansive power was still an open 

 question. It is singular that after 

 the great number of experiments 

 made there is so little known. A 

 new series of experiments have 

 been ordered by the government, 

 and it would perhaps be better to 

 postpone the further discussion of 

 this question until after the results 

 of the new experiments are known. 



or the next discussion was "Harbor Defence." 



Ends Stevens, Secretary pro tern. 



'■\ 



American Institute Polytechnic Association. 



March 12, 1863. 



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



The Chairman. — There is, probably, no better illustration of the unde- 

 veloped resources of the country, than in the immense business that has, 

 within a few years, sprung up in the petroleum or oil trade. 



The following is the trade of one city alone — Pittsburg: 



To the oil district of the United States, the city of Pittsburg occupies 

 a central position; her river navigation, that cheapest of transportation, 

 reaches all the principal oil producing regions, and to Pittsburg tlie crude 

 oil naturally came for a market. The necessity of refining the petroleum 

 before it could be used for burning, led to the immediate demand for refin- 

 eries. The low price of fuel at Pittsburg, and the cheapness of construct- 

 ing the iron work necessary for their erection, caused them to be at once 



