108 
CAPTAIN NOBLE AND MR. F. A. ABEL ON FIRED GUNPOWDER. 
construction of this instrument has been fully explained elsewhere, we shall only here 
give a very general description of it. 
Its most recent form is shown in plan and elevation in Plate 18. figs. 1 & 2. The 
mechanical part consists of a series of thin disks, A, A, &c., 36 inches in circumference, 
keyed on to a shaft, S, and made to rotate at a very high and uniform velocity through 
the train of wheels F, by means of a very heavy descending weight at B, arranged, to 
avoid an inconvenient length of chain, upon a plan originally proposed by Huyghens. 
This weight is continually wound up by means of the fly-wheel and handle at T. The 
stop-clock D, which can be connected or disconnected with the shaft E at pleasure, 
gives the precise speed of the circumference of the disks, which is usually arranged at 
about 1250 inches a second. 
The recording arrangement is as follows : — Each disk is furnished with an induction- 
coil, G, the primary wire from which is conveyed to any point, K, in the gun where we 
may wish to record the instant at which the shot passes. There is at each such point a 
special contrivance by which the shot in passing severs the primary wire, thereby causing 
a discharge from the secondary, which is connected with the discharger, Y. The spark 
records itself on the disk by means of paper specially prepared to receive it. The 
instrument is capable of recording the millionth part of a second, and, when in good 
working order, the probable error of a single observation should not exceed 4 or 5 one 
millionths of a second. 
The guns were arranged for the experiments as shown in fig. 3 in the same Plate. 
Holes were drilled in the powder-chamber in the positions marked A, B, C, and in the 
bore in the positions marked 1 to 18. 
In A, B, and C crusher-gauges were always placed ; the holes numbered 1 to 18 were 
fitted with crusher-gauges or the chronoscope-plugs at option. 
It would be beside our object in this paper to enter into a discussion of the special 
experiments undertaken by the Committee of Explosives. The chief object of their 
investigations was to determine the nature of powder most suitable for use with heavy 
guns — that is to say, the powder which will allow of the highest effect being realized 
without unduly straining the structure within which the explosion is confined. A number 
of experiments were therefore made with powders of abnormal types, interesting and 
instructive only to artillerists ; and these experiments will doubtless be fully reported on 
at a later date, by the proper authorities. 
In our present paper we shall confine our attention chiefly, if not entirely, to the 
results obtained with the well-defined and well-known powders which have been admitted 
into the service for use with rifled guns, and which are known under the names of “Rifled 
Large Grain” and “ Pebble.” These powders are, moreover, the same as were used by 
us in our experiments in closed vessels, and therefore allow of a strict comparison with 
the tensions so obtained. But before giving the details, we cannot pass without notice 
certain differences in the results obtained by means of the two modes of experimenting 
to which we have alluded. 
