A square table of cast-iron supports a shaft, upon one end of which is the usually formed fast and loose pullies to receive motion from the propelling power by a band. On the opposite end is a fly wheel, also of cast-iron. In the centre of this shaft, between the two journals on which it turns, is an eccentric, formed within the diameter of the shaft, and connected with the bridle (to be noticed hereafter,) by a stub-end and strap, constructed in the usual manner. Front view of the Cutting-out Press.

The table supports also two columns, upon which rests a kind of architrave, forming a seat for the die, to which the latter is secured by two hooks with screws and nuts. Above each column is a circular guide rod, for the cross head, which is made of bell metal. In the centre of the cross head is the bed for the punch, with a follower closing upon it, and secured by two screws. Over the cross head passes the bridle, which is constructed of iron in one piece, and is secured to the cross head by a cap. By means of this bridle the motion of the eccentric, (which does not exceed three-eighths of an inch,) is communicated to the cross head and punch; the latter descending into the bed a short distance, when the eccentric is at its lowest point.

To the bed of the die is attached a stripper, guide, and stop. The first serves to draw the strip off the punch, when the latter rises; the second to guide the strip laterally; and the last to determine the distance to which the strip is pushed forward, so as to ensure regularity, and of course economy, in cutting out the greatest number of pieces that the strip is capable of yielding.

Cutting out presses on this principle are rapid and efficient in their operation; they will cut out 160 pieces, or more, per minute, and are not subject to derangement; and finally require very little power to move them, the momentum of the fly being sufficient to pierce the slip when running at the rate mentioned above.

These cutting-out presses were made by Messrs. Merrick and Agnew of this city, and we have great pleasure in stating that in exactness of execution, beauty of finish, and general style of workmanship, they are satisfactory in the highest degree. In these respects they are not surpassed by any machines of foreign or domestic execution. The presses, milling machines, and some other of the apparatus for the Branch Mints, have been executed by the above firm, to all of which these remarks are equally applicable.

It is proper here to mention, that when the first press was constructed, Mr. Rufus Tyler was a member of the firm, and had the superintendence of this part of the work.

Mr. Samuel Raub's Safety Apparatus for Steam Boilers.
(Communicated for this Journal by Prof. W. R. JOHNSON.)

This igenious, but simple and efficient plan for indicating the deficiency of water in a steam boiler, is presented in the accompanying sketch, (fig. 1.)

D is a vertical section through the length of a cylindrical steam boiler, without an interior flue; m n is the ordinary water line, and op is the fire line of the same boiler. On the top of the cylinder is riveted a plate of brass e, serving for valve seats, and through the centre of this plate passes the upright iron pillar g, with a fork at top to receive and support, on an axis, the lever B. On opposite sides of the axis, and at equal distances from it, are attached to the lever the rods of the two equal valves v and v' the former of which opens inwards, and the latter outwards, so that any pressure of steam within the boiler which tends to open the one, tends by an equal force to close the other; but any force which is applied to either arm of the lever, tends to affect both valves in the same manner. h is a simple guide rod, in the slit of which the lever plays, and k a guide for the valve rods on the inside of the boiler. A is a solid, or hollow, metallic body,

having, from its form when hollow, a specific gravity rather greater than that of water, and is kept, generally, quite immersed in the liquid, but when from any cause left uncovered by the water, it tends to descend by a force which is measured by the weight of such a bulk of water as there may be of the solid laid bare. Thus if there be one cubic foot of the solid above the level of the water, the force it will exert to open the valves will be about sixty-two pounds. This equality between the bulk of the body uncovered and the weight of water which measures its gravitating power, is the consequence of being counterpoised by the weight C, which, under ordinary circumstances, is just sufficient to keep the valves at their seats, when A is completely immersed. It is evident that as the valves are similar, and of opposite tendencies when urged by the steam, and as they are attached at equal distances, on opposite sides of the fulcrum of the lever B, they are, under all circumstances of pressure in the boiler, equally prone to obey any external force, and as the relation between the specific gravity of water and that of an immersed incompressible solid is not changed by the circumstance of both being under a pressure of steam, no impediment is felt to the action of the valves when the steam is up, more than when the boiler is filled with cold water and common air.

It is true, the relation of the specific gravity of the solid, and of the steam in which it is immersed when not covered with water, is changed with the pressure of steam; because, unless surcharged with heat, the latter has its density increased in proportion to the pressure, but the relation between the density of water at all known temperatures, and of steam at any working pressure, is such as to preclude the supposition that the buoyant power of the latter can ever become sufficiently important to modify the action of the immersed body. Thus, since water is 815 times heavier than common air, the latter will buoy up a body immersed in it, 1-815th part as much as the former fluid. Hence, any solid immersed, and floating indifferently in water in vacuo, at 60° and then raised above its surface, would there weigh one eight hundredth part more than if raised into a medium of the density of common air; but if raised into a medium having the density of common steam, that is, vapour which counterpoises the pressure of the atmosphere, it would weigh only one 1696th part less than when raised out of water into a vacuum. If the steam into which it might be raised were at a pressure of two atmospheres, the weight lost by a change from a vacuum to steam of that tension, would be nearly 1-848th of the whole weight; and if of ten atmospheres, 1-169th of the same amount; and as the last mentioned pressure is probably above the mean working pressure of high pressure boilers, it is evident that the greatest difference between the effect of the immersed body when tried in atmospheric air, and in high pressure steam respectively, would be only about one half of 1-170, or one 340th of the weight of water which is equal to its bulk. This in the case of a float having a bulk of one cubic foot, would be less than one fifth of a pound. Hence, if an apparatus of this kind be properly adjusted at common temperature, and while the steam chamber is yet filled with atmospheric air, it would not be sensibly diminished in efficacy by a pressure of steam of twenty atmospheres, or twice as great as the highest working pressures now deemed useful in the steam engine. With regard to the form of the immersed body, the inventor has not restricted himself, but practice will doubtless indicate the propriety of making its vertical dimension small, so that when the water once comes down to its upper surface, its whole bulk may become as speedily as possible uncovered, and effective towards opening the valves. This condition

must, however, be made consistent with the free escape of steam, generated below the immersed body, to the steam chamber above; hence a division of the body into several distinct portions, united by inflexible bars, may sometimes be found expedient.

P

Fig. 2. represents the form and action of the apparatus in a common cylindrical boiler. The depth of the body A is about the same as the distance between the lowest safe water line and the highest fire line outside of the boiler; it might be as much less than this, as it should be found convenient to make it, and its upper surface should, when suspended in the water, be coincident with that of the water at the moment it has come down to the level just indicated. In this figure the apparatus is represented as in action, the same as in fig. 1.

In fig. 3 is seen a vertical section of the apparatus, such as may be used in cylindrical boilers, with interior flues. Two distinct portions of the immersed body, A A, are united by an inflexible rod, curved upwards to conform, when required, to the exterior of the flue d. This arrangement facilitates the escape of steam generated by the top part of the flue. The marks for water lines and fire lines are the same as in figs.

1 and 2.

Fig. 4 represents a tubular boiler, with the immersed body formed of a series of pieces of tube, closed at both ends, and connected together by

rods into a kind of grate-formed assemblage as more distinctly seen in fig. 5. The tubes used in this apparatus may be of the same diameter as those constituting the boiler, or of any less size, affording ample freedom for the escape of steam through their interstices, in its passage from the boiler tubes below, to the steam chamber above.

In figs. 2, 3 and 4 the interior valve only is exhibited; the rest of the apparatus being entirely the same, whatever is the form of the immersed body, or of the boiler in which it is used.

Description of an Apparatus for conveying orders to Steamboat Engineers. By A. C. JONES, Engineer.

TO THE COMMITTEE ON PUBLICATIONS.

Gentlemen-Being impressed with the imperfection of the method now in use on board of steamboats, for conveying information to the engineers, i. e. by the use of two bells of different tone, the ringing of one being frequently mistaken for that of the other, from which injurious consequences have frequently arisen, I took the liberty, in the early part of this year, to forward to the Secretary of the Navy, a plan for the more perfect management of the engines on board of the steam batteries, about being built by government; this, or some similar scheme, I think would be of decided advantage on board of all steamboats.