d with a
culverin that fired a 20-pound iron ball. At point-blank the first
shot ranged 200 paces. At 45-degree elevation it shot ten times
farther, or 2,000 paces.... If the point-blank range is 200 paces,
then elevating to the _first_ position, or a tenth part of the
quadrant, will gain 180 paces more, and advancing another point will
gain so much again. It is the same with the other points up to the
elevation of 45 degrees; each one gains the same 180 paces." Collado
admitted that results were not always consistent with theory, but it
was many years before the physicists understood the effect of air
resistance on the trajectory of the projectile.

_Sights_ on cannon were usually conspicuous by their absence in the
early days. A dispart sight (an instrument similar to the modern
infantry rifle sight), which compensated for the difference in
diameter between the breech and the muzzle, was used in 1610, but the
average artilleryman still aimed by sighting over the barrel. The
Spanish gunner, however, performed an operation that put the bore
parallel to the gunner's line of sight, and called it "killing the
_vivo_" (_matar el vivo_). How _vivo_ affected aiming is easily seen:
with its bore level, a 4-pounder falconet ranged 250 paces. But when
the _top of the gun_ was level, the bore was slightly elevated and the
range almost doubled to 440 paces.

To "kill the _vivo_," you first had to find it. The gunner stuck his
pick into the vent down to the bottom of the bore and marked the pick
to show the depth. Next he took the pick to the muzzle, stood it up in
the bore, and marked the height of the muzzle. The difference between
the two marks, with an adjustment for the base ring (which was higher
than the vent), was the _vivo_. A little wedge of the proper size,
placed under the breech, would then eliminate the troublesome _vivo_.

During the first half of the 1700's Spanish cannon of the "new
invention" were made with a notch at the top of the base ring and a
sighting button on the muzzle, and these features were also adopted by
the French. But they soon went out of use. There was some argument, as
late as the 1750's, about the desirability of casting the muzzle the
same size as the base ring, so that the sighting line over the gun
would always be parallel to the bore; but, since the gun usually had
to be aimed higher than the objective, gunners claimed that a fat
muzzle hid their target!

[Illustration: Figure 47--SEVE