envelope. In the other types the keel is in reality a chain of
rigid links similar to that of a bicycle. The form of the
envelope is maintained by the internal pressure and not by the
keel, but the resistance of the latter to compression enables a
lower pressure to be maintained than would be possible in a
purely non-rigid ship.

The M type ship is of considerable size, the P smaller, while the
D.E. is a small ship comparable to our own S.S. design. The
review of these three countries brings the early history of
airships to a conclusion. Little of importance was done
elsewhere before the war, though Baldwin's airship is perhaps
worthy of mention. It was built in America in 1908 by Charles
Baldwin for the American Government. The capacity of the
envelope was 20,000 cubic feet, she carried a crew of two, and
her speed was 16 miles per hour. She carried out her trial
flight in August, 1908, and was accepted by the American military
authorities. During the war both the naval and military
authorities became greatly interested in airships, and purchased
several from the French and English. In addition to this a ship
in design closely resembling the S.S. was built in America, but
suffered from the same lack of experience which we did in the
early days of airship construction.

We must now see what had been happening in this country in those
fateful years before the bombshell of war exploded in our midst.



CHAPTER III