6 
Lieut. Col. Miller’s description of a percussion shell, 
tried, and narrow ones were found not to answer. They 
must he of suflficient width to expose their sides, upon which 
the air presses, to its action throughout their length. For, if 
the air has not a free passage through them (Plate I. fig. 2) it 
will act as backwater on a mill-wheel. It is upon this principle 
that the blades of a windmill will not act if placed against a 
wall; and that rifles with very narrow grooves are found not 
to answer. In the beginning of 1822, some further experi¬ 
ments were made at Woolwich. On the first occasion, 10 
grooved leaden musket balls were fired from a plain barrel 
through a target, at the distance of 100 yards. The balls 
were well finished, but heavier behind than before; and from 
the marks left by them in the target in passing through it, 
two of them appeared to have turned in their flight From 
the circular holes left in the target by the others, they ap¬ 
peared to have passed through without turning. In the next 
experiment, balls of a somewhat better construction were 
employed. Several were fired at 40 yards, into a mass of 
boards and clay prepared for the purpose; and out of the 
number so fired, three or four were found in the exact posi¬ 
tion in which they lodged, all point foremost. 
A grooved wooden shot was then fired six times from a 5-^ 
inch howitzer, against a bank, at 50 yards. This experiment 
distinctly pointed out the necessity of balancing the two ex¬ 
tremities, as that which was heaviest showed an evident 
tendency to drop lower and lower during the flight. 
A wooden shot of the same form and proportions was then 
fired from the same gun, with a 3 lb. iron shot in its centre. 
This being properly balanced flew very steadily, hit the 
target, and then split without passing through it, but leaving 
