176 Chronographs and their Application to Gun Ballistics. [May 1, 



WEEKLY EVENING MEETING, 



Friday, May 1, 1896. 



William Crookes, Esq. F.R.S. Vice-President, in the Chair. 



Colonel H. Watkin, C.B. E.A. 31.B.I. 



Chronographs and their Application to Gun Ballistics. 



The lecture I have had the honour of being asked by the Council of 

 this Institution to give to-night, is on a subject in which I have taken 

 great interest and worked at for the last twenty-five years. ^ There is 

 a fascination in being able to record minute portions of time which 

 our senses are not able to discriminate. It is easy to talk about 

 the millionth of a second, but it is hard to realise how small this is. 

 To try and convey some idea of this, supposing a man were to work 

 eight hours every day, Sundays excepted, for close upon seven years, 

 one-millionth of his working time during that period would be 

 represented by ono minute. The instrument which I hope to show 

 you at work this evening records to that accuracy when working at 

 tbe highest speed. The objects I had in view in designing the appa- 

 ratus are twofold. First, the measurement of the velocity of a 

 projectile outside the gun, or external ballistics. Secondly, the 

 measurement of the velocity of a projectile at dififerent parts of the 

 bore of a gun, or internal ballistics. The first is useful for comparing 

 the relative power of different guns, merits of different powders, and 

 for determining the resistance of the air. The second for ascertain- 

 ing the pressure exerted at different parts of the bore by different 

 natures of powder, from which the shape of the gun is determined. 

 I dare say you have all noticed the very different shapes of modern 

 guns from those of a few years ago. This difference is due to the very 

 different behaviour of the powder, or rather propellant, now employed, 

 as one can hardly talk of cordite as powder. 



I propose this evening to very briefly describe some of the older 

 forms of chronographs, and more minutely describe those on the table, 

 which I have designed for experiments in ascertaining the velocity of 

 a shot passing through the bore of a gun. 



The subject divides itself into two principal parts : — 



1. The apparatus for measuring minute portions of time. 



2. The appliances for utilising these instruments for ballistic 

 purposes. 



