cylinder and ram of the ordinary hydraulic press. The Hydraulic Mattress consists of a square or circular water-tight vessel or flat bag formed of 1/2-inch thick iron or steel plates securely riveted together; its dimensions being, say 15 feet square by 3 feet deep, and having semicircular sides, which form enables the upper flat part of the Mattress to rise say to the extent of 6 inches, without any injury to the riveted joints, as such a rise or alteration of the normal form of the semicircular sides would be perfectly harmless, and not exceed their capability of returning to their normal curve when the 6-inch rise was no longer necessary, and the elevating pressure removed.

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• The action of this gigantic press is as follows. The Mattress A A having been filled with water, an additional quantity is supplied by a force pump, capable of forcing in water with a pressure of one ton to the square inch ; thus acting on an available surface of at least 144 square feet surface -- namely, that of the upper flat surface of the Mattress. It will be forced up by no less a pressure than twenty thousand tons, and transfer that enormous pressure to any article that is placed between the rising table of the press and the upper table. When any object less thick than the normal space is required to receive the pressure, the spare space must be filled with a suitable set of iron flat blocks, so as to subject the article to be pressed to the requisite power.

As before stated, there may be many processes in the manufacturing arts in which such an enormous pressure may be useful; and this can be accomplished with perfect ease and certainty. I trust that this account of the principles and construction of such a machine may suggest some employment worthy of its powers. In the general use of the Mattress press, it would be best to supply the pressure water from an accumulator, which should be kept constantly full by the action of suitable pumps worked by a small steam-engine. The great press would require the high-pressure water only now and then; so that it would not be necessary to wait for the small pump to supply the pressure water when the Mattress was required to be in action.

A Tapping Square, or instrument by which Perfect Verticality of the Tapping of Screwed Holes is insured.

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• The letter X shows how Screws are frequently made when tapped in the old mode; the letter T as they are always made when the Tapping Square is employed.

A Mode of turning Segmental Work in the Ordinary Lathe

In executing an order for twenty locomotive engines for the Great Western Railway Company, there was necessarily a repetition of detail parts. Many of them required the labour of the most skilful workmen, as the parts referred to did not admit of their being executed by the lathe or planing-machine in their ordinary mode of application. But the cost of their execution by hand labour was so great, and the risk of inaccuracy was so common (where extreme accuracy was essential), that I had recourse to the aid of special mechanical contrivances and machine tools for the purpose of getting over the difficulty. The annexed illustration has reference to only one class of objects in which I effected great saving in the production, as well as great accuracy in the work. It refers to a contrivance for producing by the turning- lathe the eighty bands of the eccentrics for these twenty engines. Being of a segmental form, but with a projection at each extremity, which rendered their production and finish impossible by the ordinary lathe, I bethought me of applying what is termed the mangle motion to the rim of a face plate of the lay, with so many pins in it as to give the required course of segmental motion for the turning tool to operate upon, between the projections C C in the illustration.

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• I availed myself of the limited to-and-fro horizontal motion of the shaft of the mangle motion wheel, as it, at each end of the row of pegs - in the face plate (when it passes from the exterior to the interior range of them) in giving the feed motion to the tool in; the slide rest, "turned" the segmental exterior of