EXPERIMENTS ON SOLID AND GASEOUS EXPLOSIVES. 



363 



spring S must be made longer, the ratio of its cross-sectional area to that of the 

 piston must be decreased, and the knife-edges 2 and 3 be brought closer together. 



In fig. 3 the design of the actual instrument is given, the lettering being the same 

 as in the previous figure. 



By means of the thread U the gauge screws into the explosion chamber, the end 

 C of the piston being flush with the inside surface. An air-tight joint is formed by 



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LJ LJ 



01 234 56789 10 



SCALE /N INCHES. 



Fig. 3. Recording manometer. 



the ring U on the manometer pressing against a flat ledge in the enclosure (see 

 fig. 5, a). The end of the gauge from D to E is a good fit in the walls of the explosion 

 chamber, and the joint is thus protected from the direct effect of the explosion. 



The spring S, about 5 inches in length, is tubular in shape. To prevent any 

 buckling it is made to closely fit the cylinder, in which it is contained, at two places, 

 e l and e 2 . The spring is fixed at the outer end Z, being held in place by the nut K ; 

 at the inner end it is free and supports the piston P. The copper gas check used in 

 the crusher gauge is replaced by a leather washer, attached to the piston by the 

 screw C and to the fixed part of the gauge by the ring E. The end of the piston 

 projects by about one-hundredth of an inch, and it can therefore move back, by this 

 amount, without straining the leather. 



The mirror (not visible in the figure) is carried by the lever L. This lever is so 

 designed that the knife-edges 1, 2 and 3 (see fig. 2) are in the same plane, it being at 

 the same time possible to bring the knife-edges 2 and 3 within one-hundredth of an 

 inch of each other, should so great an amplification be found necessary. Up to the 

 present, however, the distance has not been decreased below one-sixteenth of an inch, 

 the scale obtained with this distance being found sufficiently large. 



The actual working of this type of recorder has proved very satisfactory. Its time 

 period is sufficiently small to allow records to be obtained not only of the curve of 

 rise of pressure of the fastest cordite, but also of the rapid vibrations which modify 

 the curve under certain conditions.* 



* Captain BRUCE KINGSMILL has proposed the application of this gauge to ballistic work with a view to 

 " indicating " a gun in much the same manner as we now indicate a steam engine. This suggestion, which 

 might lead to valuable results, has, as far as I am aware, not yet been carried out in practice. 



3 A 2 



