lbs. or more per square foot of area; which resulted in great
increase in speed. Although a speed of 126 miles per hour had
been attained by a specially designed racing machine over a short
distance in 1914, the average at that period little exceeded, if
at all, 100 miles per hour; whereas in 1918 speeds of 130 miles
per hour had become a commonplace, and shortly afterwards a speed
of over 166 miles an hour was achieved.

In another direction, also, that of size, great developments
were made. Before the War a few machines fitted with more than
one engine had been built (the first being a triple
Gnome-engined biplane built by Messrs Short Bros. at Eastchurch
in 1913), but none of large size had been successfully produced,
the total weight probably in no case exceeding about 2 tons. In
1916, however, the twin engine Handley-Page biplane was
produced, to be followed by others both in this country and
abroad, which represented a very great increase in size and,
consequently, load-carrying capacity. By the end of the War
period several types were in existence weighing a total of 10
tons when fully loaded, of which some 4 tons or more represented
'useful load' available for crew, fuel, and bombs or passengers.
This was attained through very careful attention to detailed
design, which showed that the material could be employed more
efficiently as size increased, and was also due to the fact that
a large machine was not liable to be put through the same
evolutions as a small machine, and therefore could safely be
built with a lower factor of safety. Owing to the fact that a
wing section which is adopted for carrying heavy loads usually
has also a somewhat low lift to drag ratio, and is not therefore
productive of high speed, these machines are not as fast as