11)18] 



Internal Ballistics 



303 



WEEKLY EVENING MEETING, 

 Friday, May 24, I'Jls. 



Henry E. Aiimstoxg, LL.D. F.R.S., A^ice-President, in the Chair. 



LiEUT.-CoLONEL A. G. Hadcock, K.B.E. F.R.S. 



Internal Ballistics. 



The object of the lecture was to draw attention to a recent view of 

 the behaviour of modern propellants when ignited in a gun. It 

 was pointed out that Benjamin Robins in his " New Principles of 

 Gunnery," published in 1742, gave an indicator diagram (see Fig. 1) 



DIAGRAM FROM ROBINS* 

 NEW PRINCIPLES OF GUNNERY. 1742 



Fig. 1. 



of the pressures developed by the powder gas along the bore of a 

 gun. Robins assumed that the temperature of the inflamed powders 

 was the same as that of red-hot iron, and concluded from the amount 

 of gas produced from a unit weight of powder as ascertained by 

 Hawksbee, that the pressure of the gas, just before the shot moved, 

 was 1000 atmospheres, or 6'6 tons per square inch. Subsequently 

 Dr. Hur.ton proved that this estimate was much too low, and that it 

 might be doubled at least. 



According to modern views, when the charge is ignited in a 

 breech-loading gan a somewhat complicated series of incidents occur. 



(1) The charge begins to burn at atmospheric pressure. 



