ESTABLISHED 1853. HOWSON & SON'S OFFICES FOR PROCURING United States and Foreign Patents AND PROSECUTING PATENT CAUSES. HENRY HOWSON, Engineer and Solicitor of Patents. CHARLES HOWSON, Attorney-at-Law and Counsel in Patent Cases. Principal Office, 119 South Fourth Street, Philadelphia. Branch Office, 605 Seventh St., Washington, D.C. Authors of "The American Patent System," "Our Country's Debt to Patents," "Answers to Questions of the State Department Relating to Patents." Also, of a "Brief Treatise on Patents," published by Porter & Coates. United States & Foreign Expert in the Trial of Patent Causes. Examinations in regard to the Validity and Infringement of Patents. Rejected Cases a Specialty, Offices, 901 Walnut St., Dec., '79 1 yr PHILADELPHIA. THE Franklin Institute is not responsible for the statements and opinions advanced by contributors to the JOURNAL. EXPERIMENTS ON THE COMPRESSION OF AIR BY THE DIRECT ACTION OF WATER. By J. P. FRIZELL, C.E. Some ten years ago, the writer's attention was called to the compressing of air for mechanical purposes by causing it, in the form of minute bubbles, to be carried downward in a current of water and lodged in a receiver by changing the direction of the current from vertical to horizontal. Such a method appeared to promise important advantages over existing methods of utilizing water power, putting it in a form to be transmitted to distant points and allowing the location of mills and factories to be chosen without reference to the requirements of water wheels. The application of this method on a scale corresponding to a high degree of efficiency would involve a large expense and its entirely novel and experimental character seemed to render hopeless any attempt to bring it to the notice of capitalists. Nothing was therefore done in the way of its development beyond theoretical researches and some crude and simple experiments till within a couple of years. Public attention was first called to the subject in a paper published in the JOURNAL OF THE FRANKLIN INSTITUTE for September, 1877, in which the theory of the method was set forth and its probable WHOLE NO. VOL. CX.-(THIRD SERIES, Vol. lxxx.) 11 advantages pointed out. This had the effect to excite the interest of a prominent New England manufacturer, Gen. J. C. Palfrey of Boston, at whose expense the experiments to be detailed have been mainly conducted. It was well understood that a practically satisfactory efficiency could not be obtained from a model. With a low velocity, narrow passages and small head, the resistances bear a large proportion to the motive power, and may even absorb it altogether. Theoretical considerations indicate that the efficiency increases with these several elements, till it may in certain conditions reach as high as 80 per cent. or even higher. The apparatus first tried is represented in Fig. 1. Two glass tubes, B and C, were passed through the cover of a strong glass vessel, the fittings being, as near as possible, air-tight. The tube B terminated at the upper end in a siphon, and dipped into a tub, A, kept nearly full of water. The tube Copened into another tub, D. The tube B had a small orifice at the summit, closed by a flap valve, ing the air. There was another minute orifice at o. The two tubs being filled with water as indicated by the dotted lines, the water, of course, filling the receiver and rising in the tube B to the level of the for exhaust surface in the tub D, the siphon was set in action by placing the finger over the orifice o, and exhausting the air by applying the mouth to the summit orifice, then closing the latter. The flow was kept up by dipping the water from the lower to the higher tub. The pressure within the tube at the point o being a little less than that of the atmosphere, the air enters there and is carried downward by the current and lodged in the receiver. This device worked very well as an illustration of the method. The quantity of air collected in the receiver was very small. No attempt at an exact estimate of the useful effect was made. It was very slight, probably not over 5 per cent., certainly not over 10 per cent. of the power expended. The diameter of the tubes was 14 inches. The air accumulated under a pressure of 8 or 9 feet of water. The head or difference of level between the two tubs was 8 to 12 inches. No difficulties not previously foreseen being developed by this experiment, it was decided to try the method on a larger scale. For this purpose the apparatus represented in Fig. 2 was constructed. The receiver was of cast iron, circular, 2 feet diameter, 2 feet high. The pipes B and C were of iron 3 inches diameter inside. The water was supplied from a wooden tank in two compartments, A, D, the flow being maintained by pumping the water from the lower to the higher level, with a small centrifugal pump driven by steam, which does not appear in the cut. The pipe B terminated, as before, in a siphon, or rather this time, in two siphons, provided at their summits with connections for an air pump to set them in action. The air was admitted, as before, through minute orifices, o, o, just above the surface of the water in the chamber A. A glass gauge on the receiver showed the quantity of air contained in it. The pressure of the air is measured by a column of water equal to the height of the surface in the chamber D above that in the receiver. This apparatus was exhibited at the fair of the charitable Mechanic Association in Boston, in 1878. It was afterwards set up in the laboratory of mechanical engineering at the Massachusetts Institute of Technology, and became the subject of critical experiments by Professor Whitaker and members of his class. The quantity of water was inferred from the velocity of the pump. The velocity could also be observed, but not very closely, in the descending shaft, which, near the bottom, was of glass. From the best data attainable, Mr. Whitaker computed the efficiency at 263 per cent; that is, the power repre sented by the air after compression is but 26 per cent. of that represented by the water employed in compressing it. The head in this experiment was about 25 inches. This result, though at once accepted by the unthinking as a failure of the method, was so entirely in accordance with the true theory of the subject that it strengthened our confidence and induced us to make a trial upon a larger scale. In the meantime I had been called by business to St. Paul, Minn. The application of this method on any greater than the laboratory scale requires conditions very rarely met with, viz.: a deep pit, free from water, in the immediate vicinity of a small waterfall. These conditions happened to be presented at the Falls of St. Anthony, on the Mississippi river a few miles above St. Paul. A vertical shaft was sunk by the United States Engineer Department, several years since, in the work for the preservation of the falls, and had never been refilled. It was about 36 feet deep and was drained by a pipe opening into the river below the falls. Its clear dimensions, inside the timbering, were about 6 X 14 feet. It occupied a narrow island between two mill ponds, one of which was maintained some 8 or 10 feet higher than the other. Permission to occupy this shaft for the purpose in question was readily given by the officer in charge of works in this district, C. J. Allen, Captain of Engineers, and Dr. S. H. Chute, one of the managers of the St. Anthony Water Power Company, kindly gave permission to use the water and make the necessary excavation for races. The apparatus, except the raceways, is shown in Figs. 3, 4 and 5. Figure 3 is a vertical longitudinal section; Fig. 4 a cross section through the air chamber, and Fig. 5 a plan. The apparatus consists of a strong wooden tank at the bottom of the pit, with two vertical shafts or channels rising to the surface of the ground. The shaft for the descent of the water, in which. a considerable velocity is required, is 15 × 30 inches. The ascending shaft, whose function is to return the water to the surface with as little loss of head as possible, is 24 × 48 inches. The upper part of the tank between the vertical passages is occupied by the air chamber which is lined with zinc and is furnished with a cock, f, operated from above, as shown, for the escape of air. The air chamber is separated from the passage below it by a partition of boards laid with openings which allow the air to pass freely into the chamber. It will be noticed that the descending shaft, at the bottom, is contracted strongly in the plane of the section, though it expands |