A door, whereof the turning of a key, with the help and motion of the handle, makes the hinges to be of either side, and to open either inward or outward, as one is to enter or to go out, or to open in half. NOTE. By making the handle act on a lever communicating with the hinges, they may be raised from their sockets on the required side; and to open in half, it is merely necessary to joint them in the centre. No. LXXV. How a tape or riband-weaver may set down a whole discourse, without knowing a letter, or interweaving any thing suspicious of other secret than a new-fashioned riband. NOTE. The evident analogy between this Article and No. XXXIII. will be apparent on the slightest view, and in general principle it is similar to Nos. XXXIV. XXXV., &c. It may be performed either by making the stitches of a given length, varying the distance to distinguish the different letters of the alphabet; or, by any arbitrary shape which may be previously agreed upon by the parties corresponding. These arrangements being made, the silk weaver will have nothing more to do, than set his loom to the required pattern. No. LXXVI. How to write in the dark, as straight as by day or candle-light. NOTE. Two planes of ebony of equal length and breadth, similar to the parallel ruler, and joined at each end by racks, the side of which being graduated to the width of the line intended will serve as a certain guide, and by the use of this instrument a blind person may write with the greatest accuracy. If ivory tablets or a slate is used, a fine wire drawn with a steel point may be readily felt by the point of the pencil. No. LXXVII. How to make a man to fly: which I have tried with a little boy of ten years old, in a barn, from one end to the other, on a hay-mow. NOTE. Innumerable are the schemes that have been proposed by the learned at different periods, to enable man to support himself in the air by the means of artificial wings, &c. and some, indeed, of these ingenious contrivances have formed the labours of the most distinguished mechanical geniuses, which are recorded in the early annals of science. Bacon, and an Italian priest named Francisco Lana, endeavoured to accomplish it by means of two thin hollow globes, exhausted of air, which being considerably lighter than that fluid, were intended to sustain a chair suspended to their lower extremity, and on which the aeronaut might be seated. But Dr. Hook, in a work published some time after the _Prodromo_ of Lana, plainly showed the fallacy of the attempt, though without in the least attempting to deny the possibility of eventually effecting this object.