PROCEEDINGS: WASHINGTON SOCIETY OF ENGINEERS l8l 



element a number of time intervals between the closing of the firing 

 circuit and the ejection of the shell from the gun. It is only necessary 

 to so arrange the circuits that each event will produce a characteristic 

 record on the film. 



To obtain a record of a motion which is continuous, such as the re- 

 coil of the gim, a step-by-step method has been adopted. This consists 

 of a series of contacts so arranged that at definite distances there will 

 be a sudden change in the resistance of the circuit. This will produce a 

 small but definite movement of the oscillograph element so that the 

 time when this occurred is recorded on the oscillograph film. Then, 

 from the known positions of the contacts, and the measured times, 

 a curve can be plotted which will show the rate at which the movement 

 took place. 



This step-by-step method has the advantage that both the distances 

 and the time can be accurately measured. Hence, at the points where 

 the change in resistance takes place, the position and time are deter- 

 mined with a high degree of accuracy. If a curve is plotted, using time 

 and position as coordinates, this curve is very accurate at all points, 

 excepting where the motion is changing direction. If the total motion 

 is known, the curve can be made accurate at this point also. 



The above method has been used in the design of a recoil-meter. 

 The steps are not the same throughout the entire length of recoil, but 

 are shorter during the first part of the curve and longer during the latter 

 portion. This increases the accuracy during the first part of recoil 

 where a study of the motion of the gim is most important. Very satis- 

 factory curves have been obtained. 



The same principle has also been employed in the design of a kine- 

 meter, which is an instrument for obtaining the motion of the gun in a 

 direction perpendicular to its axis. This instrument is designed on the 

 same principle as a seismograph, and has also given satisfactory^ results. 



This paper was illustrated by lantern slides, and was discussed by 

 Messrs. L. J. Briggs, White, Hawkesworth and Hull. 



The meeting adjourned at lo.io and was followed by a social hour. 



S. J. Mauchly, Recording Secretary. 



WASHINGTON SOCIETY OF ENGINEERS 



Fourteen meetings of the Society were held during the year 1919, as 

 follows : 



January 15, 1919: Charles R. Mann, Professor of Education and 

 Director of Educational Research, Engineering education. 



February 5, 1919: Major C. H. West, Chemical Warfare Service, 

 U. S. Army, Use of poisonous gases in modern warfare. 



February 19, 1919: Brigadier-General Samuel T. Ansell, Acting 

 Judge Advocate General of the Army, Relationship of the engineer to the 

 Army. 



