g made in France, and it was only after I had
seen these tubes that I seriously considered the question of making a
flying machine. I obtained a large quantity of them and found that they
were very light, that they would stand enormously high pressures, and
generate a very large quantity of steam. Upon going into a mathematical
calculation of the whole subject, I found that it would be possible to
make a machine on the aeroplane system, driven by a steam engine, which
would be sufficiently strong to lift itself into the air. I first made
drawings of a steam engine, and a pair of these engines was afterwards
made. These engines are constructed, for the most part, of a very high
grade of cast steel, the cylinders being only 3/32 of an inch thick,
the crank shafts hollow, and every part as strong and light as possible.
They are compound, each having a high-pressure piston with an area of
20 square inches, a low-pressure piston of 50.26 square inches, and a
common stroke of 1 foot. When first finished they were found to weigh
300 lbs. each; but after putting on the oil cups, felting, painting, and
making some slight alterations, the weight was brought up to 320 lbs.
each, or a total of 640 lbs. for the two engines, which have since
developed 362 horsepower with a steam pressure of 320 lbs. per square
inch.'

The result is remarkable, being less than 2 lbs. weight per horse-power,
especially when one considers the state of development to which the
steam engine had attained at the time these experiments were made. The
fining down of the internal combustion engine, which has done so much to
solve the problems of power in relation to weight for use with aircraft,
had not then been begun, and Maxim had nothing to guide him, so far
as work on the part of his predecessors was concerned, save the
experimental engines of Stringfellow, which, being constructed on so
small a scale in comparison with his own, afforded little guidance.
Concerning the factor of power, he says: 'When first designing this
engine, I did not know how much power I might require from it. I thought
that in some cases it might be necessary to allow the high-pressure
steam to enter the low-pressure cylinder direct, but as this would
involve a considerable loss, I constructed a species of injector. This
injector may be so adjusted that when the steam in the boiler rises
above a certain predetermined point, say 300 lbs., to the square inch,
it opens a valve and esc