Ittttru to thr thitur.
CAPTAIN ERICSSON'S CALORIC-ENGINE.
1, Adam Street, Adelphi, 28th January 1833. Sin-Various accounts have appeared in the columns of the Times, copied from American journals, respecting the wonders achieved by the caloric vessel of Captain Ericsson. One very remarkable statement appeared to- day-" That there was a saving of nine-tenths of the fuel as compared with steam."
If this be true, it will prove only that steam-engine builders are so ig- norant of their art as to waste nine-tenths of their fuel. They would be very glad to see this made out, because it would open up a very wide scope for improvement. If Captain Ericsson can do it with en air-engine, by a process of taking up his heat after it has done its work, and using it over again, similar processes may also be applied to steam. For, call them by what names we will, they are both heat-engines, giving forth power by the con- sumption of fuel, or the conversion of solids into gases-i. e. enlarging the volume of matter by swelling it with particles of heat, the matter being is one case air and in the other case water. A perfect steam-engine is supposed to waste no heat whatever. All the heat generated in the furnace should pass into the boiler, and so furnish power to the cylinders, except so much as it is needful to pass up the chim- ney in order to produce draught and urge the fire. If more than is needful passes away thus, it is waste, and an evidence of faulty construction. 'Heat may radiate very rapidly from the boilers, the chimney, and the cylinders; and the greater the pressure of the steam the greater will be the ration. For this reason, the boilers of locomotives, worked at high pressure, are clothed in felt and wood and metal, and the cylinders likewise, unless when covered within the smoke-box or base of the chimney. Whenever great heat is ex- perienced in the engine-roem of a vessel, it is a proof of so rod& waste ; and the use of a wind-sail to cool the room, although it may diminish the an- noyance, does not diminish the waste. A hot Oimney is a large source of -waste and an evidence of ill-regulated draught. There is, no doubt, much room for improvement yet. Boilers clothed so as to prevent radiation, and chimnies constructed with double plates and an interstice of air between, would save much waste, and increase comfort and diminish risk. If radia- tion were entirely prevented, and draught economically regulated, there would be no advantage in a dry calorie over a wet caloric machine. But Captain Ericsson, it appears, catches his heat after ithas done its work in the cylinder, turns the air out nearly cold, and then uses the same heat to inject other air, and pass again through the cylinder. A similar process is used in the steam-engine. High-pressure steam, after having impelled the piston of a small cylinder, is turned in an expanded state into a larger cylinder, and the heat does duty twice. There is an advantage in high-pressure steam, that a smaller space is occupied by the engines and boilers with a given amount of power ; the con- sumption of coal being the same. Nor does it follow that the risk is greater. A boiler worked at four pounds pressure may get short of water and explode, as well as one at one hundred pounds pressure ; and with a given thickness of plate the small boiler is stronger than the large one. in Ericsson, however, claims the advantage of gettingrid of explosion altogether. If it should turn out that he gets rid of power at the same time, the advantage would only be of the same kind as using a gun without charg- ing it. If a cylinder of fifty inches area be worked at a pressure of one hundred pounds per inch, we have a power of five thousand.pounds. To get the same result with a pressure of four pounds, would require a cylinder with an area of twelve hundred and fifty inches. What we really want to know is—the also of the cylinders and the effective pressure in them, the number of strokes per minute, and the weight and quality of the coal used per. our. If the heat can be used over again to the extent that has been vaguely al- luded to, we shall be very near perpetual motion ; lighting a fire in the har- bour of New York, and using the heat over and over again till we reach England, with perhaps an occasional scuttle of hot coals from the galley. Captain Ericsson is not the.man to propound such things, and his friends are not judicious to do it for him. There was a caloric-engine in the Great Exhibition, but it was never worked. The pressure claimed then was four pounds per inch : I have heard that eleven pounds is now -claimed. The heat-catcher, as described, appears to be a sort of gigantic respirator, such as is worn over the mouth in cold weather.
" They drank the red wine through the helmets barred." As the wires of the respirator catch the warmth of the breath in passing from the mouth, so the cylinder exit is barred with heat-catchers. In loco- motive cylinders the exits for the steam can scarcely be made too large ; and any attempt to catch the steam, to compel it to disgorge its heat, would be fatal to the velocity : so if a wire cap be placed on a chimney, the draught is impeded. Why the caloric-engine should not be subject to the same law does not yet appear. ' By the description, the caloric-engine appears to be very similar in etruc- tare to the old atmospheric steam-engine, but with four-pound pressure air substituted for four-pound pressure steam. Whether the saving of the boil- ers and space be not counterbalanced by other ciroumstances remains to be seen : but it must be quite clear, that if any advantages are to be gained by the mere saving of waste, that applies to the steam as well as the calorie engine.
P.S.—Since this was written, another voice from New York proclaims that the uniform pressure is 12 pounds and the diameter of the cylinders 14 feet; but that the vessel is a comparative failure, because they should have been 16 feet, and that if they were 20 feet " the vessel would outstrip the speed of anything that now floats on the water." This description, to use the words of an American witness, "is about as big as a piece of chalk." We have the further information, that "the -machinery was not tight, and was only working at half power." So that we are to expect a pair of 20 feet cylinders, with a pressure of 24 pounds per Mob, when "the engines are put into a state of completeness previous to her trip to Baltimore."
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