Bibliography. 181 
This pendulum is a-counterpart to the gun, as regards its mode of ‘sus- 
pension and motion, which is also measured in like manner on a grad- 
uated arc. This ‘ dock’? as it is called, resembles a mortar or wide 
howitzer, with a bore of four and a half feet deep and fifteen inches 
calibre, and filled with leathern bags of sand, and a bedding of lead: 
This block, the frame and counterpoise weights, weighed 9,358 Ibs., and 
was suspended so as to hang when at rest, with its axis perfectly in one 
and the same line as the axis of the gun. When prepared for use 
the aperture of the pendulum block was covered by a sheetof lead, 
which served to make the deviation of the ball from a right line, by 
the hole which was pierced in it. This deviation was found to be very 
slight. 
It seems, to a person unaccustomed to such experiments, a tnthor 
daring attempt to fire a thirty-two pound shot, at the distance of only 
fifty feet into the mouth of another gun. But that velocity which left 
unrestrained, would serve to carry the shot for miles, is in this apparatus 
restrained within the range of a few feet, and imparts only a moderate 
motion on the great mass of matter on which it impinges, which can be 
wholly and accurately estimated. Capt. Mordecai remarks that ‘“‘an 
observer placed in such a position as to see the face of the block un- 
obscured by the smoke of the gun, perceives at the moment of im- 
pact, a circle of reddish white flame surrounding the hole made by the 
ball.” He supposes “‘ that this flame may be produced by the combus- 
tion of minute particles of iron and lead ignited by friction.” He fur- 
ther remarks, that “ in firing a thirty-two pound ball into the pendulum 
block with a charge of eight pounds, the sand immediately before the 
ball was compressed into a solid mass, forming an imperfect sandstone 
sufficiently firm to. bear handling. A specimen is still preserved in that 
state after a lapse of more aa pightoer:. apt e his sand when 
examined, was found quite _ An appa- 
ratus of quite similar ‘structure, on a proportionate scale, was used for 
muskets. In these experiments powder from a great number of man- 
ufactories, and of great variety of composition, grain and finish, were 
tested. The elements for calculating the strength of gunpowder, ob- 
tained by these experiments, were resolved by the formule of Hutton 
and those which more recently have been employed by the French at 
Metz. This portion of the labor is performed with the accuracy and 
skill, which characterize all the highly educated officers from West Point 
Academy: Capt. Mordecai concludes from the results of his experi- 
ments, that the only reliable mode of proving the strength of gunpow- 
der is to test it, with service charges, in the arms for which it is designed; - 
for which purpose ‘the balistic pendulums are perfectly adapted. 3 
