Various methods have been heretofore described, for raising heavy bodies, or producing for other purposes, a great force,--usually miscalled power--by the application of a comparatively small force: but no method is known, more unlimited in its effect, or more simple in construction; than the conical windlass. It consists of a simple horizontal windlass, with a crank at one end, as shown in the engraving. The windlass is made in a conical form, being a little larger at one end, than at the other; and if the friction of its bearings be relieved by the ordinary friction rollers, it will so far multiply the force applied, as to break a double inch-rope, by the power of one man at the crank. An endless rope, or one of which the two ends are spliced together, is passed five or six times round the small end of the windlass, and down under a single pulley below: then, as the windlass is turned by the crank, the rope is constantly given off from one part, while the circumference is greater. Now it is plain, that if the windlass is one-fifth of an inch larger in circumference, at the point at which the rope is taken up, than at the place where it is given off to the pulley, that whatever may be appended thereto, will be raised one tenth of an inch by each revolution Then, if we suppose the crank lever to be fifteen inches, the handle will travel about 100 inches, in each revolution, which gives a power, or increase of force, of 1000 to one. Therefore, if 100 pounds of power be applied to the crank handle, it will be sufficient--minus friction--to raise a weight of 100,000 lbs. The only inconvenience in this apparatus, and which prevents its coming into more general use, is, that it is too limited in the extent of its motion, in consequence of the travelling of the rope from one end of the windlass to the other. Thus, if the windlass be but twenty-five inches long, and the rope one inch in diameter, it will admit only twenty revolutions, without renewing. Yet, in many cases, in which an article in required to be raised, or moved but a few inches, the conical windlass will be found preferable to any other method. * * * * * REQUISITE STRENGTH OF STEAM BOILERS.