I do not apprehend that any considerable resistance would be offered by the internal air, and the motion of the wheel can be regulated by its load, so as to offer a sufficient resistance to the descending stream of water; and I, therefore, assume that the water, in its descent, would produce by means of the wheel, a power capable of raising a part of the water expended back again to the cistern; and this is the extent of the power of most of those machines which have been mistaken for perpetual motions by their projectors. But I have a blast of wind which is described as being of great force. Can this blast be in any way applied to raise the surplus water? I think I see the smile which the proposal will produce in those who deny the possibility of a perpetual motion. "A mere puff of wind!" is doubtless ejaculated from all sides. But let me tell these gentlemen that, though I may not know any method by which such blast can produce that effect, it does not, by any means, follow that the impossibility of the thing is thence to be presumed. Far from it; for such a conclusion rests upon the supposition that the powers and application of a blast of wind are fully known, and that no research or experience can add to our knowledge on that subject--assumptions which appear to me somewhat ridiculous. Allow me, for the sake of argument, to suppose that this blast instead of wind, had been a blast of steam. Time was when wise men would have smiled and said, "A puff of steam--a mere puff of steam!"--and had some one, more sanguine than the rest, attempted by its application to produce a motion, he would have applied it to the floatboards of a wheel, as in Branca's engine, and have been disappointed. It is not given to man to know when the powers of any great agent have been fully developed; and those who act upon such presumptions throw the greatest obstacles in the way of inquiry. But, to show the anti-perpetualists that within their own time since the commencement of the "Mechanics' Magazine," an addition has been made to our knowledge of the powers of a blast of wind, I have added a tube, G, to my figure, the proposed use of which I shall now describe. In a part of the "Mechanics' Magazine," published some time ago, there was described a novel mode of raising water in a tube by directing a stream of air over its mouth, thereby destroying the pressure of the atmosphere.