PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 56o 



thing spinning around its axis tends to keep its position, without 

 thai motion it tends to deviate from its course. The effect of 

 feathering an arrow is to keep the end back and the point forward. 

 An Illinois man patented a ball with grooved sides to act on the 

 air. The twisting of the ball should be caused before it leaves 

 the gun, and not after it. It is not possible in practice to make 

 the centre of mass and the centre of gravity coincide. E? 

 thought it might be advisable to twist the ball only once in a 

 hundred f<^.et. 



Dr. Yander Weyde said that the fact of all revolving bodies 

 holding their axial positions with the same force with which they 

 moved in a straight line, was originated by Isaac Newton. 



The Chairman referred to a gun once tested by the Government 

 which requires three charges of powder. He wished to know the 

 inventor. 



Mr. Seely said it was a Mr. Haskell. 



The Chairman. — Is there anything gained by the powder reach- 

 ing the ball in three successive discharges ? 



Mr. Garvey thought there was a decided loss. The first charge 

 is fired, and the gas is in a state of undulation, and what will be 

 the result of these successive undulations when the gas gene- 

 rated coincide? 



Mr. Haskell said there was a difficulty in having guns too long. 

 He thought a barrel of two feet long would answer all purposes. 



Mr. Johnson said that the best kind of guns made in this coun- 

 try were made with a three hours fusion, (i. e., the iron kept in 

 the fusion state for three hours before casting.) 



Adjourned to Thursday evening next, January 31st, 1861, at 7 

 o'clock, when the subject of " Fuel " will be discussed. 



American Institute, Polytechnic Association, )' 

 January 31, 1861. ] 



Mr. Wm. Lawton in the chair. . 



Mr. Bruce read the following paper on projectiles : 



I will now proceed to give a description of two projectiles 

 which I deem of a terrific character, with the construction of 

 which I was somewhat connected. 



The first was a bomb invented by my son, Wm. D. Bruce. It 

 consisted of a shell of cast iron of any desired thickness, sus- 

 pended in the centre of which was another shell of about a third 



