On commencing the study of .aeronautics it is above all things most important that we should make ourselves thoroughly acquainted with what has already been accomplished in order to save waste of effort on our part in trying experiments or devices already dealt with. Again, it is quite a mistake to suppose that but little, if anything at all, has as yet been accomplished towards the solution of this—the, perhaps, greatest of all mechanical problems. We do possess at last a science, of aeronautics, and a preliminary study of this same science is a sine quâ non; the successes and failures of the past must be carefully studied, as also the apparent causes of such successes and failures; and the principles involved— that is to say, the aerodynamical principles— must be above all things, most carefully studied, in order that the investigator may be perfectly enabled to distinguish between any inadequate proposal, certain to fail, and a design worthy of consideration, investigation, and, perhaps (after careful thought), a practical trial.