the inclination is only 1 in 20, but experiments have shown that this theory is very wide of the truth. There are dozens of ways of showing, by pure mathematics, that Newton’s law is quite correct; but in building a flying machine no theory is good that does not correspond with facts, and it is a fact, without any question, that the lifting effect of an aeroplane, instead of increasing as the square of the sine of the angle, only increases as the angle. Lord Kelvin, when he visited my place, was, I think, the first to mention this, and point out that Newton’s law was at fault. Professor Langley also pointed out the fallacy of Newton’s law, and other experimenters have found that the lifting effect does not increase as the square of the sine of the angle. In order to put this matter at rest, Lord Rayleigh, who, I think we must all admit, would not be likely to make a mistake, made some very simple experiments, in which he demonstrated that two aeroplanes, in which we may consider the sine of the angle to be 1/4 inch, lifted slightly more than a similar aeroplane in which the sine of the angle was only 1/2 inch. Of course, Lord Rayleigh did not express it in inches, but in term of the radius. His aeroplanes were, however, very small. We can rely upon it that the lifting effect of an aeroplane at any practical angle, everything else being equal, increases in direct proportion to the angle of the inclination. In this little work, I have attempted to make things as simple as possible; it has not been written for mathematicians, and I have, therefore, thought best to express myself in inches instead of in degrees. If I write, “an inclination of 1 in 20,” everyone will understand it, and only a carpenter’s 2-foot rule is required to ascertain what the angle is. Then, again, simple measurements make calculations much simpler, and the lifting effect is at once understood without any computations being necessary. If the angles are expressed in degrees and minutes, it is necessary to have a protractor or a text-book in order to find out what the inclination really is. When I made my experiments, I only had in mind the obtaining of correct data, to enable me to build a flying machine that would lift itself from the ground. At that time I was extremely busy, and during the first two years of my experimental work, I was out of England fourteen months. After having made my apparatus, I conducted my experiments rather quickly, it is true, but I intended later on to go over them systematically and deliberately, make many more experiments, write down results, and prepare some account of them for publication. However, the property where I made these experiments was sold by the company owning it, and my work was never finished, so I am depending on the scraps of data that were written down at the time. I am also publishing certain observations that I wrote down shortly after I had succeeded in lifting more than the weight of my machine.