This is the genuine court plaster. It is pliable, and never breaks, which is far from being the case with many of the spurious articles which are sold under that name. Indeed, this commodity is very frequently adulterated. A kind of plaster, with a very thick and brittle covering, is often sold for it. The manufacturers of this, instead of isinglass, use common glue, which is much cheaper; and cover the whole with spirit varnish, instead of balsam of Peru. This plaster cracks, and has none of the balsamic smell by which the genuine court plaster is distinguished. Another method of detecting the adulteration is to moisten it with your tongue _on the side opposite to that which is varnished_; and, if the plaster be genuine, it will adhere exceedingly well. The adulterated plaster is too hard for this; it will not stick, unless you moisten it on the varnished side.--_The Painter, Gilder, and Varnisher's Companion_. * * * * * AN IMPROVED HOISTING PULLEY WANTED. A gentleman of this city has sent us the accompanying diagram of an improved hoisting pulley, for which he say she would be willing to pay any reasonable price provided he knew where to obtain it--the wheel, not the price. It is a pulley within a pulley, the friction of the outer one upon the inner one--the latter being held by a ratchet and pawl-acting as a brake in lowering weights, while both would turn together in elevating weights. The idea is rather an ingenious one, but we are confident our inventors can attain a like object by simpler means. [Illustration] * * * * * THE VACUUM METHOD OF MAKING ICE.--An ice and cold producing machine has been invented by Herr Franz Windhausen, Brunswick. The action of the machine is based on the principle of producing cold by the expansion of atmospheric air, which is accomplished by means of mechanical power. The machines require no chemicals, nothing being used in them but water and atmospheric air. They may be wrought by steam, water, or wind, and they produce from 100 to 1,000 lbs. of ice per hour, according to size, at a cost of from 2d. to 5d. per 100 lbs., this difference resulting from the varying prices of fuel and the mode of working chosen. One of their uses is to cool rooms, cellars, theaters, hospitals, compartments of ships, etc.--_Builder_. * * * * * FERDINAND DE LESSEPS--CHIEF PROMOTER OF THE SUEZ CANAL. [From the Phrenological Journal.]