Although pressure engines operated by air compressed under a head of water, as suggested by Papin in 1695, had been employed success fully to drain mines as early as 1755, when Hoel employed one in the mines of Chemnitz, Hun gary, the application of steam for that purpose did not become an accomplisheed fact until a much later period. It is, however, interesting note that the idea was suggested by Lord Bacon prior to 1679, in connection with the Eng lish mines, and probably was practically applied to a limited extent about that time. The his tory of the modern pumping engine, however, more properly begins with the construction of the Cornish engine. Up to the close of the 18th century, the only practical use of steam engines was in connection with pumping devices, and many notable steam pumping engines had been erected and successfully operated in the mines of Cornwall, England. The various improve ments made in this engine from 1800 to 1840 finally culminated in the evolution of one su perior type which is now known as the 'Cor nish?) This engine gave highly satisfactory service for the particular purpose for which it was designed — the raising of water out of deep mines where the constantly increasing depth of the shafts necessitated the adaptation of the same engine to the consequent increasing and changing loads. It is constructed upon the principle that the steam within the steam cylin der is used to lift a weighted pump plunger which after being raised upward to the limit of its stroke, descends slowly by its own weight and forces upward a column of water equal to that weight. The economy produced by the expansion of the steam in the steam cylinder when the steam is cut off during the descent of the plunger is due to the fact that the pressure and power of the steam first admitted is greatly in excess of what is necessary to lift the weighted plunger. This excess of power is taken up by the weights of the plunger at the beginning of its stroke and given out at the end when the power of the exhausted steam in the cylinder has fallen below the amount neces sary to move the plunger, unless assisted by the power previously stored in it. The length of the stroke of the piston and of the plunger being determined solely by the operation of its steam, equilibrium and exhaust valves, it is absolutely necessary to maintain the steam pressure at a uniform rate, while the water raised must be received under a uniform head. In mine pumps the steam cylinder is placed at the top of the shaft, and the pump at the bottom, near the surface of the water. The steam piston is connected to the pump plunger by a beam made of heavy timbers, the weight of which, together with that of the weight of the plunger, forms the weight which, after being lifted by the steam cylinder, raises an equal weight of water when the plunger descends.
In order to preserve the proper relation be tween the weight of the pump rods and plunger, and that of the water columns, and also keep the engine and pump at the proper speed, by maintaining the proper difference in the weight of the pump rods so as to overcome the friction of their guides, and that of the water in the delivery pipes, a large box, called the ((balance bob,' in which the adjusting weights in the shape of stones or pieces of iron are placed, is attached to the upper end of the pump rods. When the shafts become deeper and require the lengthening of the pump rods, the additional weight of the new timbers is counterbalanced by a readjustment of the weights in the ((balance bob' thus adapting the engine to the new con ditions. In its particular field of application, re quiring only a slow action with no demand for continuous flow, it is safe to state that it has never been excelled by any other engine; but, its inordinate size, its action which requires the constant watchfulness of the engineer, its great first cost and expensive repairs, makes it unfit for waterworks, where the water has to be dis charged through a long main to a great height above the pump, with a continuous and uniform delivery. The shortcomings of the Cornish en gine, named above, led finally to its complete abandonment for waterworks, and called for a pumping engine that would fulfill the new re quirements. This demand was met by the de velopment of the ((rotative) engine which, by employing revolving instead of reciprocating pistons, gave a positive motion. The steam power in the cyhnder is applied to the pump piston in various ways — through the medium of long or short beams, bell cranks or gearing, and in some instances directly through the pis tons themselves; in all cases, however, the limit of the stroke of the steam piston and of the pump plunger being governed by a crank on a revolving shaft. Attached to this shaft is a
fly-wheel which is designed to assist the crank to pass the centre at each end of its stroke and also to give up at the beginning of each stroke of the steam piston the excess of power im parted to it beyond that required to move the column of water. The function of the fly-wheel of a rotative engine is exactly similar to that of the weighted plunger in a Cornish engine; both of the devices being applied to their respective classes of engines to obtain the best economy in the consumption of steam, the early cut-off resulting in a high grade of expansion, much higher than it was possible to obtain by any other means at the time. They vary greatly in design and in the details of construction, and are made in sizes ranging from those used for supplying water to small towns, up to some of the largest and most expensive machines in the world, and operate either vertically or hori zontally. They produce great economy in the use of steam at the expense of intricate ma chinery, but require expensive and massive foundations to absorb the shocks produced by their operation, while the momentum of the fly wheel greatly increases the percentage of possi ble accidents.
To follow further the progress of pumping engine construction up to the invention and de velopment of the °direct-acting steam pumps,) which now represent the highest type of pump lug machinery, it is necessary to take up the historical thread in the United States. Al though steam pumping engines of the direct acting type, beginning with the device invented by Thomas Newcomen and John Cawley, of Dartmouth, England (which was subsequently improved by Watt, who developed it into an engine of the double-acting type), were in great use for many years; the greatest improvement in this class of pumping engines was made by Henry R. Worthington of New York in 1840. His invention was the outcome of a long series of experiments on the application of steam to the propulsion of canal boats. It was a single direct-acting steam pump and was employed to feed the boilers of his propelling engine, and was patented for the first time in 1841. Al though steam pumps of this type came imme diately into extensive use for feeding boilers and for supplying moderate quantities of water under medium pressure, the intermittent action of their pump pistons and consequent irregular flow of water prevented them from being used in waterworks and for other purposes where large quantities of water had to be forced through long lines of pipes. To overcome this serious defect the same inventor produced the improved pump which is now generally known by his name.
Bibliography.— Butler, E. (Modern Pump ing and Hydraulic Machinery (London 1913) ; Davey, H., 'Principles, Construction • and Ap plication of Pumping Machinery) (London 1905) ; Greene, A. M. 'Pumping Machinery> (New York 1911) ; Hague, C. A., (Pumping Engines for Waterworks) (New York 1907); Kelley, H. H., (Pumps: Including the Air-Lift Pump> (Atlanta, Ga., 1915) ; Nickel, F. F., (Di rect-Acting Steam (New York 1915).
Revised by RICHARD FERRIS.
a play upon words alike or similar as to sound, but different as to sense. The pun has been familiar to all literatures, and in an cient times was used even in serious context. This was true also in England of the 17.th and 18th centuries. Puns are met with in the trage dies of Shakespeare; in the works of the quaint Fuller i in the discourses of Bishop Andrews. The divines of colonial America did not lack for them. Mathey Byles won his reputation for wit chiefly through the appositeness and felicity of his puns. Thus, being a sturdy loyalist, he was for a time kept under surveillance by a sentinel whom he called his
A parishioner called upon him and Byles, not ing his ulcerated jaw, sent him to Copley, the artist, to have his tooth drawn. Among famous English punsters may be cited Sydney Smith, Lamb Theodore Hook, Wilberforce and, above all, 'Tom') Hood, most inveterate and happy of the coterie, who even remarked of a certain undertaker that he appeared anxious to "win a lively Hood.* The pun has frequently been de rided as an unworthy form of wit. John Donne is reported to have said that "He who would make a pun would pick a pocket)); and Holmes, in the