Scientific American Volume 22, No. 1, January 1, 1870 Part 1

Scientific American, Vol.22, No. 1, January 1, 1870.

by Various.

Engines of the Spanish Gunboats.

In our description of these boats in No. 25, Vol. XXI., special mention was made of the compactness of the engines.

It has frequently been urged as an objection against the twin screw system that the double set of engines, four steam cylinders with duplicates of all the working parts called for on this system, render the whole too complicated and heavy for small vessels, preventing, at the same time, the application of surface condensation. In the engines of the Spanish gunboats, of which we annex an ill.u.s.tration from _Engineering_, the designer, Captain Ericsson, has overcome these objections by introducing a surface condenser, which, while it performs the function of condensing the steam to be returned to the boiler in the form of fresh water, serves as the princ.i.p.al support of the engines, dispensing entirely with the usual framework. Besides this expedient, each pair of cylinders have their slide frames for guiding the movements of the piston rods cast in one piece. Altogether the combination, is such that the total weight and s.p.a.ce occupied by these novel twin screw engines do not exceed the ordinary single screw engines of equal power. Several improvements connected with the working gear have been introduced.

[Ill.u.s.tration: ENGINES OF THE TWIN SCREW SPANISH GUNBOATS]

The outer bearings of the propeller shafts, always difficult to regulate and keep in order on the twin screw system, are selfadjusting and accommodate themselves to every change of the direction of the shafts.

This is effected by their being spherical externally, and resting in corresponding cavities in the stern braces or hangers. The spring bearings for supporting the middle of the shafts are also arranged on a similar self-adjusting principle.

The thrust bearing is of peculiar construction, the arrangement being such that the bearing surfaces remain in perfect contact however much the shaft may be out of line. The reversing gear likewise is quite peculiar, insuring complete control over the movement of the two propellers under all circ.u.mstances. It is claimed that these engines are the lightest and most compact yet constructed for twin screw vessels.

The Torpedo Boat Problem.

The _Army and Navy Journal_ thinks the problem of a torpedo boat capable of firing rapidly and with certainty, has at length reached a satisfactory solution. It says:

"A boat has been completed which is proved by experiment to be faultless in machinery and arrangement. On the 2d of December, Secretary Robeson, Vice-Admiral Porter, and Commodore Case, Chief of the Bureau of Ordnance, went to the Navy Yard at Washington, to witness the experiment with this new engine of destruction. After examining the workings of the machinery, and the manner of firing, one of the destructives was put in the frame and the party proceeded to the sh.o.r.e to witness the result. A torpedo of only thirty-six pounds was first run out with rapidity and fired; but the result showed that this small amount of powder, even, would have been sufficient to destroy any ship, by lifting her out of the water and breaking her back, even if her bottom was not knocked out altogether. Mud and water were thrown up together, and the concussion was felt far up in the Navy Yard, the ground being shaken by the shock of the powder against the bed of the river. The concussion felt on board the torpedo-boat was not more than that caused by a wave striking a vessel at sea.

"Several torpedoes were fired from the vessel, the explosion of which the party witnessed on board, as they desired to ascertain for themselves the effect of the shock. The result seemed satisfactory, as no change whatever is contemplated in the machinery, which is very simple, and 'works to a charm.' The torpedo vessel is the _Nina_, a very strong iron boat of three hundred and fifty tuns burden, capable of crossing the ocean, and having a speed of seventeen knots an hour. She is not impervious to heavy shot, but can be made so, and is capable of resisting any ordinary projectile that could be brought to bear on her from the decks of a ship of war. Her decks will be made torpedo and shot-proof, and several arrangements will be applied, now that it is known that the torpedo system is a success. Such a vessel as the _Nina_, attacking an enemy's squadron on our coast some dark night, or entering an enemy's port, could destroy half the vessels in the harbor, and easily escape as few vessels could overtake her. Such a vessel could, for instance, enter the harbor of Havana, and destroy every vessel of war in the port, under cover of darkness. A squadron supplied with such boats to be used to attack, after the fight began, and the ships were enveloped in smoke, would have a most decided advantage against an enemy not thus armed for torpedo warfare. It is reported that our torpedo navy will consist of twenty vessels, none of which will have a less speed than twelve knots, and the fastest of them will go seventeen knots."

SUGAR MAKING IN LOUISIANA.

The New Orleans _Times_ contains, in a late number, an account of the manufacture of sugar as conducted on the Poychas estate, from which we extract portions containing the essential particulars of cane sugar making as conducted in the southern portions of the United States.

"Reaching the Cane shed, the crop, dumped into piles, is received by a crowd of feeders, who place it (eight or ten stalks at a time) on the cane carrier. This is an elevator, on an endless band of wood and iron, which carries them to the second story, where the stalks drop between the rollers. An immense iron tank below, called a juice box, receives the liquid portion, and another elevator bears the bruised and broken fragments to the opposite side of the building, where they are dropped into the baga.s.se burner.

"This invention, at its introduction, caused more scientific inquiry and dispute, probably, than any other of the age, and settled beyond question the possibility of combustion, without the use of atmospheric air. The process consists in dropping the wet, spongy ma.s.s into a fire of wood or coal, and closing the furnace doors. The steam arising from the drying matter pa.s.ses to a chamber in the rear, where, by the intense heat, it is decomposed. Oxygen and hydrogen (both strong combustibles) unite with the carbon, reaching there in the form of smoke, and a white heat is the result.

"Cane juice, as it escapes from the mill, could scarcely be considered inviting to either palate or vision. The sweet, slimy ma.s.s of fluid, covered with foam, and filled with sticks, has more the appearance of the water in a brewer's vat than anything which now suggests itself. A small furnace, containing a quant.i.ty of burning sulphur, sends through a tube a volume of its stifling fumes, and these, caught by jets of steam, thoroughly impregnate the contents of the juice box. Having received its first lesson in cleanliness, the liquid now rises through a tube to the series of clarifiers on the second floor. They are heated by a chain of steam pipes running along the bottom, and being filled, the juice slowly simmers Much of the foreign substance rises in a sc.u.m to the surface and is skimmed off by the sugar maker. It is further purified by the addition of Thomaston or what is called sugar lime. At one half a peck is considered sufficient for seven hundred and fifty gallons of juice, but much depends upon the quant.i.ty of saccharine matter it contains.

Another set of pipes now permit the liquor to run into the evaporators, in the boiling room below. These are also heated by circles of steam pipes, and the liquid is first gently simmered, to enable any additional foreign substance to rise to the surface and be skimmed off.

"After that the steam is turned on fully, and the juice boils until it reaches the solidity of twenty-five degrees, as measured by the saccharometer. This point attained, more pipes conduct it to a series of square iron tanks called filterers. Each is provided with a false bottom, covered with thick woolen blankets, and through these the juice slowly drips into an immense iron vessel called a sirup tank.

"The process of cleaning has now been completed, and the sirup is pumped into the covered vessel previously alluded to, called the vacuum pan.

"This is also heated by layers of steam pipes, and here the liquor boils until the process of crystallization is completed. This end achieved, another conductor permits the substance to slowly descend to a large square iron tank, called a strike-pan. The process of emptying the vacuum pan is technically called a "strike." We now find a reddish brown substance, having somewhat the appearance of soft mortar.

"Men are at hand with square wooden boxes, and while the sugar is still warm, it is placed in rotary cylinders, protected on the inside by wire guards, called centrifugals.

"Placed on a horizontal, they revolve with a velocity which frequently reaches 1200 a minute. The damp, dingy looking pile instantly spreads, a broad circle of yellow is first visible on the inner rim of the machine, and this slowly whitening finally becomes a shining ring of snowy sugar.

To effect this result requires the aid of nine steam boilers, three steam engines, a vacuum pan, three large evaporators, five clarifiers, five filters, an immense sirup tank, the juice box, mill, baga.s.se furnace, and fifteen coolers.

"With the engineers, sugar makers, firemen, and laborers, thirty-eight persons are constantly on duty in this sugar-house.

"Doubling this number, to give each the necessary rest, swells the gathering to seventy-six souls, who, during the grinding season, find employment at the sugar-house alone. This of course does not include the laborers employed in gathering and bringing in the crop, and the great number occupied in odd jobs and the extensive repairs which are constantly going on."

Sticking, or Court Plaster.

This plaster is well known from its general use and its healing properties. It is merely a kind of varnished silk, and its manufacture is very easy.

Bruise a sufficient quant.i.ty of isingla.s.s, and let it soak in a little warm water for four-and-twenty hours; expose it to heat over the fire till the greater part of the water is dissipated, and supply its place by proof spirits of wine, which will combine with the isingla.s.s.

Strain the whole through a piece of open linen, taking care that the consistence of the mixture shall be such that, when cool, it may form a trembling jelly.

Extend the piece of black silk, of which you propose making your plaster, on a wooden frame, and fix it in that position by means of tacks or pack-thread. Then apply the isingla.s.s (after it has been rendered liquid by a gentle heat) to the silk with a brush of fine hair (badgers' is the best). As soon as this first coating is dried, which will not be long, apply a second; and afterwards, if you wish the article to be very superior, a third. When the whole is dry, cover it with two or three coatings of the balsam of Peru.

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 isingla.s.s, 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.

[Ill.u.s.tration]

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_.