io8 



SCIENCE. 



[Vol. XIV. No. 341 



furnace ; a regenerator, composed of wire cloth of great superficial 

 area, extending from the cooler to the bottom of the reverser 

 heater ; a cooler, composed of a large number of thin copper tubes, 

 which are surrounded by water ; and a displacer piston, having 

 rhetallic "packing rings, and adapted to reciprocate within'the cooler. 

 Each working cylinder is provided with a working piston having 

 metallic packing rings. Each reverser is connected by means of 

 pipes with the working cylinders, as follows : the hot chamber 

 below the displacer piston is connected with the bottom of the 

 working cylinder directly opposite, and the cold chamber above the 

 displacer piston is connected with the top of the working cylinder 

 diagonally opposite. 



A small single-acting air-pump, having a leather-packed piston, 

 is operated by an eccentric fastened to the. main shaft. This pump 

 is used, first, to compress the air to the initial pressure required ; 

 second, to maintain the initial pressure so attained, which is sub- 

 jected to loss by leakage around the piston-rods. The regulation 

 of the speed of the engine is obtained by a balanced equalizing 

 valve of simple construction, placed in an equalizing pipe which 

 connects the top of the working cylinders together, the valve being 

 operated by a common centrifugal governor. 



The power produced is due to the energy exerted upon the 

 . working pistons by the alternate raising and lowering of the tem- 

 perature of the same mass of air within the reversers. The cooling 

 medium used is any kind of water, or a blast of air circulated 

 through the coolers. A very small quantity of water is required, 

 and the same body of water may be used over and over "again. 



In operation, the alternate raising and lowering of the tempera- 

 ture of the same mass of air is accomplished as follows : in the 

 upward stroke of the displacer piston, the mass of air in the cold 

 chamber above the piston is forced through the cooling tubes, in 

 its downward passage through which its temperature is not ma- 

 terially changed. The air then enters the regenerator, in its pas- 

 sage through which it absorbs heat which has been imparted to 

 the regenerator. It ne.xt passes over the heated surface of the 

 reverser heater, thereby becoming further heated, and enters the 

 hot chamber below the displacer piston. 



The temperature of the air in the cold chamber is about 120° F., 

 and the temperature of the air in the hot chamber is about 600° F. 



In the downward stroke of the displacer piston, the mass of air is 

 forced into the regenerator, in its passage through which it deposits 

 therein the greater portion of its heat. It then passes through the 

 cooliog tubes, where its temperature is reduced to about 120° F., 

 and then into the cold chamber above the displacer piston. There- 

 fore, at each upward and downward stroke of the displacer piston, 

 the temperature of the same mass of air is alternately raised and 

 lowered. The reversers being in duplicate, it is obvious that the 

 same alternate raising and lowering of the temperature of the dis- 

 placed ai^r would take place in one reverser as in the other, but at 

 opposite times ; that is to say, both displacer pistons being oper- 

 ated by the reverser beam, whenever cJne displacer piston is making 

 its upward stroke, the other displacer piston is making its down- 

 ward stroke. It is therefore evident, that, when the displaced air 

 in one reverser is being heated, the displacer air in the other re- 

 verser is being cooled. 



The alternate raising and lowering of the temperature of the dis- 

 placed air (in both reversers) generates a power in accordance with 

 the well-known laws of the expansion of gases, which power is 

 developed by the working cylinders, as follows : while one dis- 

 placer piston is making its upward stroke, and is heating and ex- 

 panding the displaced air, thereby producing a pressure which is 

 exerted against the bottom of the piston of the working cylinder 

 directly opposite the reverser, and against the top of the piston of 

 the working cylinder diagonally opposite, the other displacer piston 

 is making its downward stroke, and is cooling and contracting the 

 displaced air, thereby reducing the pressure against the bottom of 

 the piston of the working cylinder directly opposite the revprser, 

 and the top of the piston of the working cylinder diagonally oppo- 

 site. Thus each working piston is subjected to differential press- 

 ures, which are alternately reversed as the displaced air is alter- 

 nately heated and cooled. Thus a power is exerted to cause the 

 working pistons to have a reciprocating motion, which is changed 

 to a rotary motion by means of the working-cylinder beam and its 



connected parts to the main shaft and the fly-wheel, from which 

 the power may be taken off by a belt. A portion of the power de- 

 veloped is absorbed in the friction of the engine, and a portion is 

 used to operate the displacer pistons. The engine is designed to 

 run on an initial pressure of air of about forty-five pounds, at a 

 speed of 115 revolutions per minute. 



PRODUCTION OF ESSENCE OF LEMON IN SICILY. 



Lemons in Sicily are divided into two classes, — the true lemon 

 and the bastard lemon. The United States consul at Messina says 

 that the true lemon is produced by the April and May blooms ; the 

 bastard, by the irregular blooms of February, March, June, and 

 July, which depend upon the rainfall or regular irrigation, and the 

 intensity of the heat during the summer and winter seasons. There 

 are but three harvests of the true lemon. The first is the Novem- 

 ber, cut when the lemon is green in appearance, and not fully ripe. 

 Lemons of this cut are the most highly prized : they possess re- 

 markable qualities for keeping, and are admirably preserved in 

 boxes or warehouses from November until March, and sometimes 

 as late as May, and then shipped. The second cut occurs in 

 December and January, and the third in March and April. 



Bastard lemons present well-defined peculiarities in shape and 

 appearance : their inner skin is fine, and adheres tenaciously to the 

 fruit ; they are hard, rich in acid, and seedless. The bastard 

 lemon produced from the bloom of June is still green the following 

 April, and ripens only towards the end of July. It remains on the 

 tree over a year. The true lemon can be left on the tree until the 

 end of May or the first week in June ; but*it interferes with the new 

 crop, drops off from over-maturity, and is liable to be attacked by 

 insects. The bastards, on the contrary, withstand bad weather 

 and parasites, and they mature from June to October. 



In obtaining the essence from the lemon, the following opera- 

 tions are performed by the Sicilian workman. He peels the fruit 

 lengthwise with three strokes of a sharp knife, and lets the peel 

 fall into a tub under the chopping-block. He then cuts the lemon 

 in two, and throws it from his knife into a bucket. He works with 

 wonderful rapidity, and fills from ten to twelve tubs with peel a 

 day, and is paid about five cents a tub, weighing 77 pounds. His 

 left hand and right index are protected with bands of osnaburgs 

 or leather. Decayed fruit is not peeled. Fresh peel is soaked in 

 water fifteen minutes before the essence is extracted. Peel that 

 has stood a day or two should remain in soak from thirty to forty 

 minutes, so that it may swell and offer a greater resistance to the 

 sponge. The operative holds a small sponge in his left hand, against 

 which he presses each piece of peel two or three times, — simple 

 pressure followed by rotary pressure. The women employed in 

 this work run a piece of cane through their sponges to enable them 

 to hold them more firmly. The outside of the peel is pressed 

 against the sponge, as the oil-glands are in the epicarp. The 

 crushing of the oil-cells liberates the essence therein contained. 

 The sponge, when saturated with the essence, is squeezed into an 

 earthenware vessel which the operative holds in his lap. He is 

 expected to press the peel so thoroughly as not to overlook a single 

 cell. This is ascertained by holding the pressed peel to the flame 

 of a candle. Should it neither crackle nor diminish the brilliancy 

 of the flame, the cells are empty. This process yields, besides the 

 essence, a small quantity of juice and dregs. The separation of the 

 essence, juice, and dregs soon takes place if the vessels are not 

 disturbed : the oil floats on the juice, and the dregs fall to the bot- 

 tom. These three products derived from the peel have no affinity 

 with each other. As the essence rises to the surface, it is skimmed 

 off, bottled, and left to settle for a few days. It is then drawn off 

 with a glass siphon into copper cans, which are hermetically sealed. 

 After the essence has been expressed, a small quantity of juice is 

 pressed from the peels, which are then either given as food to oxen 

 and goats or thrown away. 



The yield of essence is very variable, and the industry is carried 

 on five months in the year. Immature fruit contains the most oil. 

 From November to April, in the province of Messina, 1,000 lemons 

 yield about 14 ounces of essence and 17 gallons of juice. An 

 operative expresses three baskets of lemon-peel (weighing 190 

 pounds) a day, and is paid at the rate of about twenty cents a 



