marks its wake, a bomb with a delay-action
fuse can be dropped upon it, the projectile not exploding until it
reaches a depth of fifty feet or so. In case the first bomb does not
score a hit, there are others to follow, with better luck perhaps.

THE IMPORTANCE OF THE "BLIMP."

Thus, it will be seen that the blimp is an important auxiliary of the
flying-machine in the pursuit of the submarines. Both together, in this
exciting sport, supplement the swift power-boats called
"submarine-chasers."

For some time the Navy Department has trained enlisted men and officers
for this work, chiefly at a Gulf port, where a school--it is no war
secret--of aviation and ballooning has been maintained. Six officers and
40 men are required for each coast station.

The Navy Department adopted for the blimp a standardized pattern, with
definite published specifications, in accordance with which contractors
turned them out in numbers. It is a sausage-shaped balloon 160 feet
long, with a great diameter of 31-1/2 feet, and containing, when
inflated, 77,000 cubic feet of hydrogen gas.

The fabric of the "envelope"--that is to say, of the gas-bag--is coated
both outside and inside with rubber. It is required that the balloon
shall not lose more than 1 per cent of its gas-content in 24 hours. When
inflated it must be able to carry (including its own weight) a total of
5275 pounds.

If the "Zeppelin" be excepted, the blimp is the most highly-developed
and scientific heavier-than-air flying machine ever devised. It has a
cruising speed of 35 miles an hour, but at a pinch can travel ten miles
an hour faster. At the "cruising" rate, it carries enough gasoline to
keep going for sixteen hours; at 45 miles, its load of "petrol" will
suffice for ten hours.

Even the best war balloons of a few years ago were at the mercy of the
winds. It is not so with the blimp. Barring storms, it is able to
navigate the air as it wishes. It can rise safely to an altitude of a
mile and a half. To furnish fuel for its engine of 100 horsepower it
carries, in two tanks, 100 gallons of gasoline.

DESCRIPTION OF THE "BLIMP."

In effect, the blimp is a combination of balloon and aeroplane. Like the
latter, it is provided with "skids" (resembling sled runners and made of
ash wood), or sometimes with bicycle wheels, for safe landing on terra
firma. When designed for sea scouting, floats--cylinders of waterproof
fabric stuffed with vegetable fibre--are attached to