196 



ELEMENTARY PRINCIPLES OF GUNNERY. 



which is expressed adverse to the 

 adoption of relief, a term used by 

 Mr. Boucher for what is commonly 

 called " opening behind." This, 

 however, will be discussed hereafter. 

 In order to show practically the 

 truth of the opinions held by Mr. 

 Boucher, the results of the gun 

 trial held at Hornsey Wood House 

 on the 4th and oth of July, 1859, 

 are here appended. It will be ne- 

 cessary to exclude from the list all 

 those guns which were fired with a 

 different charge of powder, and to 

 compare together only those of 

 which all the essential elements 

 were alike. The machine adopted 

 was merely a wooden carriage 

 (Fig. Sab) containing the gun 

 securely fixed in a horizontal posi- 

 tion. This carriage slides back- 

 wards and forwards in a frame 

 which is firmly fixed to the ground, 

 and it is attached in front to one 

 of Baiter's balances (c d), fitted with 

 a slide which registers exactly the 

 extent to which the index is drawn 

 out by the recoil of the gun. The 

 carriage is carefully padded with 

 Indian rubber to prevent injury 

 to the stock or barrels, which latter 

 are secured by the block (fg)> At 

 the trial, the carriage was made to 

 run on wheels, but it is better to 

 construct it as here represented, 

 running freely on metal slides. A 

 thumbscrew (e) in front presses the 

 carriage back till it draws out the 

 index to lOlbs., that being at least 

 the pressure with which the gun is 



