locomotives weigh from 60 to 80 tons. In the sea, the largest animal weighs about 75 tons, while the ordinary Atlantic liner weighs from 4,000 to 14,000 tons. The whale, no doubt, is able to maintain a high speed for several hours at a time, but the modern steamer is able to maintain a still higher speed for many consecutive days. As artificial machines for terrestrial and aquatic locomotion have been made immensely stronger and larger than land or water animals, so with flying machines, it will be necessary to construct them much heavier and stronger than the largest bird. If one should attempt to propel such a machine with wings, it would be quite as difficult a problem to solve as it would be to make a locomotive that would walk on legs. What is required in a flying machine is something to which a very large amount of power can be directly and continuously applied without any intervening levers or joints, and this we find in the screw propeller. * * * * * When the Brayton gas engine first made its appearance, I commenced drawings of a flying machine, using a modification of the Brayton motor which I designed expressly for the purpose; but even this was found to be too heavy, and it was not until after I had abandoned the vertical screw system that it was possible for me to design a machine which, in theory, ought to fly. The next machine which I considered was on the kite or aeroplane system. This was also to be driven by an oil engine. Oil engines at that time were not so simple as now, and, moreover, the system of ignition was very heavy, cumbersome, and uncertain. Since that time, however, gas and oil engines have been very much improved, and the ignition tube which is almost universally used has greatly simplified the ignition, so that at the present time, I am of the opinion that an oil engine might be designed which would be suitable for the purpose.