(il'N BARRELS. 



21 



against them. Steel rifle barrels are sometimes drilled out 

 of a solid bar, which must be " set" from time to time, as 

 the drill is certain to run out. As there is usually more to 

 turn, off one side, they are generally of unequal hardness, 

 and is a difficult matter to keep them straight. Steel barrels 

 are now usually rolled from twelve to fifteen-inch drilled 

 blanks, the hole in which is much larger than the intended 

 bore. The punching of shorter blanks, which were after- 

 wards rolled out into a 'barrel by two rollings, constituting 

 the patent of Deakin and Johnson, appears now to be dis- 

 continued, though very good barrels were made by the 

 process." 



The reading of Mr. Smith's paper was accompanied by 

 practical illustrations of the method "shading" barrels, 

 or detecting internal or external irregularities. Barrels, 

 straight and bent, were supported at each end, and Mr. Smith 

 explained the entire process, which has been kept very much 

 as a secret by the very few who really understand it. So 

 delicate is this test that the distortion, produced by warming 

 one side of the barrel with a common candle, was distinctly 

 perceptible. Independently of its practical utility, the 

 " shading " of a gun barrel is an exceedingly interesting 

 optical problem, which has never yet been investigated. 



