Mr. Maxim, as he then was, commenced his experiments in the early nineties. As we have already shown, he went to Nature for his guide, and in constructing his flying machine took as his analogy the flight of birds. Birds urge their way onwards in the air by reason of the strength of their wings. A flying machine must do the same by the power of its engine; and as a bird’s wings must be strong in proportion to the bird’s weight, so the strength or horse-power of the engine must stand in a certain proportion to the number of pounds it weighs. Mr. Maxim’s first task, therefore, was to discover what proportion this must be, and by his experiments he arrived at a conclusion which Professor Langley in America, working at the same task at the same time, but quite independently, had also proved to be true, namely, that the faster a machine travels through the air the greater weight it may carry; or, in other words, the quicker a body moves through the atmosphere the less tendency will it have to fall to the ground. A quick-flying bird like an albatross, therefore, flies with less exertion, and so could carry a greater weight, than a slow-moving bird like a goose. It must therefore be to the advantage of the flying machine that its engines should attain as great a speed as possible. Maxim’s next task was to construct a suitable engine. Light but powerful engines had not then reached the pitch of perfection they have now, and his results proved at the time a perfect revelation of what could be done in this direction, and led to great advances being made. [Illustration: THE MAXIM AIRSHIP.] Next came the designing of the great machine itself. It was an enormous apparatus, weighing over three tons, capable of carrying three men, and supported by no less than 4000 square feet of aeroplanes, placed one above the other. Its steam-engine was of 363 horse-power, and worked two screws of nearly 18 feet in diameter. Before such a machine could rise from the ground it must first have attained a very great forward impetus, and this it was to receive by running at a great speed on wheels along a railway track specially laid down for it. To prevent the apparatus rising unduly, a reversed rail was erected a short distance above, on which the machine would begin to run as soon as it lifted itself off the lower track. Along this railway the flying machine was tested, and it was found that as soon as a speed of thirty-six miles an hour was reached the wheels were lifted clear off the ground, and were running only upon the upper rail. On the last occasion a speed of forty-two miles an hour was attained, when the lifting power became so great that the restraining rail broke away altogether, and the great flying machine actually floated in the air for a few moments, “giving those on board the sensation of being in a boat,” until, steam being shut off, it fell to the ground and was broken.