PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 

 TABLE II. 



OF EXPERIJIENTS WITH BURNER NO. 2. 



355 



The temperature at the time was 82° Fahrenheit. 



Self-regulatin(J Windmill. 



Mr. Enos Stevens presented a plan of a windmill, in which the power is 

 to be reg'ulated by weight; but the plan could be understood only by 

 means of engravings. 



Measuring the Force of Gunpowder. 



The Chairman. — A gentlemen called on me yesterday with a newly 

 invented gunpowder, and in the course of conversation we had a discussion 

 in regard to the mode of measuring the power of powder. I will suggest 

 to the Association this plan: introduce a pipe through the wall of a strong 

 cylinder near its lower end, and, bending the pipe at an elbow, let it rise 

 by the side of the cylinder. Pour some water into the cylinder — more 

 than enough to cover the end of the pipe. Then close the cylinder perfectly 

 tight, with the exception of a hole through the cover, through which a 

 pistol may be discharged into the interior. Will not the force of the 

 powder be measured by the rise of the water in the pipe, the expansion of 

 the gases by the height to which the water rises, and the rapidity of the 

 expansion by the time in which it rises ? 



Mr. Dibben. — I should doubt the accuracy of this mode. The inertia of 

 the water would cause some time to be consumed in moving it, and during 

 this time the walls of the cylinder would be conducting heat away by con- 

 vection, diminishing the amount of expansion. I have had a good deal of 

 experience in testing powder with the ordinary eprouvetfe, and I have found 

 the results with the same samples of powder very variable, and the effect 

 of small charges a very uncertain indication of the effect of large charges. 

 The eprouvette is a small cannon with the bore very accurately turned, and 

 a chamber in the breech to hold a given quantity of powder, generally an 

 ounce. The ball is turned to fit the bore nicely, the charge is weighed and 

 poured into a chamber through a tube, so that it may all go into the 

 chamber, and the breech is made concave to fit the ball, affording no space 

 between the powder and the ball. The cannon is set at an angle of 45°, 

 and the distance to which the ball is thrown is taken as a measure of the 

 force of the powder used. But I have found that two samples of powder 

 taken from the same barrel, and from the same half pound in the barrel, 

 would throw the ball to quite different distances, varying sometimes 20 per 



