62 Modern Cannon Powder. [January, 
foot of the powder, a box made to hold that amount being 
filled by pouring the substance loosely into it; the weight 
therefore depended, to a great extent, upon the closeness 
with which the powder packed itself, as well as upon the 
absolute density of the grains. The shape of the grains, 
and the amount of glaze the powder has received, affect the 
closeness with which it packs itself, and would therefore 
lead to errors in determining the density in this way. At 
the present time the density is accurately arrived at, by 
means of a mercury densimeter, in which the weight of a given 
volume of powder is compared with that of an equal volume 
of mercury: the density of mercury (correCted according to 
the readings of a barometer and thermometer at the time) 
being known, that of the powder is easily calculated. 
In the “‘ Mortar Eprouvette” a round shot, weighing 68 lbs. 
was fired from an eight-inch mortar with a charge of from two 
to three ozs. of the powder under examination, and the range 
of the shot from the muzzle of the mortar was measured. 
The greater the range the better was the powder believed to 
be, the only limit being a low one. The fallacy of this 
belief was proved beyond a doubt as early as the year 1864, 
by comparing the velocity of shot fired with different 
powders, by means of the accurate instruments then 
generally in use for that purpose. It was then found that 
powers which gave the best results in very small charges 
fired from a mortar were often very inferior when fired in 
comparatively large charges from guns, and the immediate 
adoption of a new proof of powder, by measuring the velocity 
of shot fired under service conditions, was strongly re- 
commended. This recommendation was not, however, carried 
out until four years later, when Colonel Younghusband, the 
present Superintendent of the Government Gunpowder 
Works at Waltham Abbey, introduced the velocity proof 
which is now in force. The instrument used at Waltham 
Abbey for measuring the velocity of a shot is an ele¢tro- 
ballistic chronoscope, invented by Captain Le Bouleuge, of 
the Belgian Artillery,* which surpasses all similar instru- 
ments in simplicity and facility of manipulation, though the 
principle upon which it acts is the same as in others. In it 
electricity is employed to record the exact instant at which 
the shot passes two points at a known distance apart, a 
short space in front of the gun. From this the time occupied 
by the shot in traversing the distance between these two 
* This instrument, and the method of using it, is described in detail in a 
pamphlet by Lieut. C. Jones, Royal Artillery, Instructor Royal Gun Factories. 
Printed by order of the Secretary of State for War. 
