554 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



ingly issued. It is dated October 15, 1781. Hostilities ceased 

 on the l7tb, and the surrender was made on the 19th ; so this is 

 among the last of the military orders issued by Washington. 

 [Prof. Joy then read the order. It directs the officer to take 

 the boats out of James river and place them on wheels and send 

 them over to the head-quarters of the army before Yorktown. 

 The order directs that the boats shall be covered with boughs 

 to prevent them from being seen by the enemy.] 



Prof. Renwick. — Had I been aware of the subject of discussion 

 for this evening, I should have brought with me a model, and 

 descriptions of an armor-clad vessel. Had I done so, however, 

 I must either have postponed the exhibition of them, or have 

 trenched upon the time that has been so profitabl}'' and instruc- 

 tively occupied. May I request that the subject be continued 

 for future discussion? 



The same subject was chosen for discussion a fortnight hence, 

 and the meeting adjurned. 



American Institute, Polytechnic Association, ) 



April 17, 1862. \ 

 Prof. Chas. A. Joy in the chair. 



original experiments with superheated steam. 



Mr. Warren Rowell made some experiments, impugning cer- 

 tain conclusions made in 1850, in relation to Mr. James Frost's 

 sfame or superheated steam. 



These conclusions were, that steam at a temperature of 212* 

 under the pressure of the atmosphere, when heated apart from 

 water, had its volume doubled by the addition of 4^* of heat, and 

 that 12'^ more of heat gave an increase of an additional volume. 



Mr. Frost's experiments were made with a siphon tube, the 

 short leg of which was three inches in length, and closed at the 

 end, while the end of the long leg was left open. He introduced 

 a minute quantity of water into the short leg, and then filled 

 this leg with mercury. The tube was held with the legs extend- 

 ing vertically upward, and the water in the short leg was, of 

 course, raised by the mercury to the upper and closed end of the 

 leg. The tube was now placed in a bath of salt water — a satu- 

 rated solution, the temperature of which is 228°. The water in 

 the tube was converted into steam, which forced the mercury up 



