Proceedings of the Polytechnic Association. 933 



tlie elastic force of the gas is absorbed in giving velocity to its own 

 particles ; this causes the heat to fall, the particles being brought to a 

 state of rest again by friction. This friction develops heat, which 

 heat is precisely equal to that absorbed in expansion. The whole 

 furnishes a beautiful instance of the law of mechanical equivalents, 

 with all the operations taking place in an instant of time. 



Mr. C. E. Emery drew a diagram of the new indicator on the 

 blackboard, and explained the difference between it and another 

 which has been extensively used in this cit}'. 



The Closi^^g Houes of 1868. 



The hour for adjournment having arrived, the chairman said, in 

 conclusion : The presence and attention of a large audience prove 

 that the proceedings have been both interesting and instructive. lie 

 congratulated the regular attendants upon tlie satisfactory manner in 

 which they had spent the last evening of the closing year. The pure 

 pleasure derived from these scientific investigations will not be followed 

 by a single pang of regret, since, aside from tlieir usefulness, they pro- 

 duce on the mind itself an elevating and ennobling effect. The good 

 already achieved, he hoped, was only an earnest of what is to follow. 



The meeting was then declared to be adjourned to the following 

 Thursday. 



Janixary 7, 1869. 



Professor S. D. Tillman in the chair; Mr. C. E. Emery, Secretary. 

 The chairman opened the proceedings by reading the following 

 summary of scientific news : 



The Keupp Cannon". 



The new feature in this gun which has produced such formidable 

 results, is the enlarged chamber in which the cartridge is lodged. 

 The charge is double that first used, while the ball remains at its 

 former weight of 200 lb. When tested side by side with the 9-inch 

 Aruistrong gun, the Prussian proved greatly superior. 



Maeixe Peojectiles. 

 A paper by Mr. Whitv.-orth was read at the last meeting of the 

 British Association, on the proper form of projectiles for penetrating 

 through the water. It gave the results of numerous experiments, 



