CAPTAIN NOBLE AND ME. F. A. ABEL ON FIEED GUNPOWDER. 
61 
C. METHODS OE EXPERIMENT. 
1. Explosion-apparatus. 
We propose, in the first place, to describe the principal apparatus used in these 
investigations, and shall commence with that portion which is of primary importance, 
viz. the vessel in which the explosions were produced. Two sizes of vessels were used, 
the larger being capable of holding about 2J lb. (1 kilogramme) of powder, the other 
being about half that capacity. 
Both vessels were of the same general construction, and similar to that described in 
Captain Noble’s Lecture at the Royal Institution already referred to. A drawing of 
the apparatus is given in Plate 14. figs. 2 & 3. 
A (see figs. 2 & 3) is a mild steel vessel of great strength, carefully tempered in oil, 
in the chamber of which (B) the charge to be exploded is placed. 
The main orifice of the chamber is closed by a screwed plug (C), called the firing- 
plug, which is fitted and ground into its place with great exactness. 
In the firing-plug itself is a conical hole, which is stopped by the plug D, also ground 
into its place with great accuracy. As the firing-plug is generally placed on the top of 
the cylinder, and as, before firing, the conical plug would drop into the chamber if not 
held, it is retained in position by means of the set-screw S, between which and the 
cylinder a small washer (W) of ebonite is placed. After firing, the cone is, of course, 
firmly held, and the only effect of internal pressure is more completely to seal the 
aperture. At E is the arrangement for letting the gases escape ; the small hole F 
communicates with the chamber where the powder is fired, and perfect tightness is 
secured by means of the mitred surface (G). When it is wished to let the gases escape, 
the screw E is slightly withdrawn, and the gas passes into the passage H. 
At K is placed the “ crusher-apparatus ” for determining the tension at the moment of 
explosion. 
When it is desired to explode a charge, the crusher-apparatus, after due preparation, 
is first carefully screwed into its place, and the hole F closed. The cone in the firing- 
plug is covered with the finest tissue-paper, to act as an insulator. 
The two wires LL, one in the insulated cone, the other in the cylinder, are connected 
by a very fine platinum wire passing through a small glass tube filled with mealed 
powder. Upon completing connexion with a Daniell’s battery the charge is fired. 
The only audible indication of the explosion is a slight click ; but frequently, upon 
approaching the nose to the apparatus, a faint smell of sulphuretted hydrogen is 
perceptible. 
The difficulties we have . met with in using this apparatus are more serious than migh 
at first sight appear. 
In the first place, the dangerous nature of these experiments rendered the greatest 
caution necessary, while, as regards the retention of the products, the application of 
