Chap. 9.]

Heron's Fountain.

361

the water, the latter is compelled to ascend through the jet pipe, as shown in the cut. The water thus forced out, falls back into the basin, and running down C into B continues the play of the machine, until all the water in A is expended. The elevation to which water in A can be thus raised through a tube, will be equal to the perpendicular distance between the two orifices of C. To persons who are ignorant of the construction of these fountains, the water in the basin appears to descend, and to rise again through the jet. Such is not the fact; were it so, this machine would be a perpetual motion, or something very like one. Some persons beguiled by the apparent possibility of inducing it to ascend, have attempted the solution of that problem by a similar apparatus. We may as well confess that in our youth we were of the number. The younger Pliny seems to have fallen into the same mistake respecting a fountain belonging to his country seat.

D

A

Portable fountains of this kind might be adopted as appropriate appendages to flower gardens, and even drawing rooms. The pipes might be concealed within, or modeled into a handsome column, whose pedestal formed the lower vessel, while the upper end assumed the figure of a vase. Such an addition to the furniture of an apartment would be a useful acquisition at those seasons when the atmosphere, glowing like the air of an oven, scorches our bodies during the day, and in the evening we gasp in vain for the cooling breeze at such times a minute stream of water spouting and sparkling in a room would soon allay the heat and invigorate our drooping spirits-imparting the refreshing coolness of autumn amid the burning heats of summer; and if the liquid were perfumed with attar of roses, or oil of lavender, we might realize the most innocent and delicious of oriental luxuries. The play of such a fountain might be continued for two or three hours at a time, for the size of the stream need hardly exceed that of a thread, and by a slight modification, the jet could be renewed as often as the upper vessel was emptied, by simply inverting the machine: or, the whole might be arranged without, except the ajutage and the vase in which the jet played. (See remarks on fountains in the fifth book.)

B

No. 163. Herou's
Fountain.

This fountain has been named a toy, but it is by such toys that important discoveries have been made in every age. It is clearly no rude or imperfect device: not a first thought; on the contrary, it bears the evidence of a matured machine, and of being the result of a familiar acquaintance with the principles upon which its action depends. Unlike older hydraulic machines, it requires no distinct vessel within which to raise a a liquid; nor does it resemble pumps, since neither cylinders, suckers, valves or levers are required, nor any external force to keep it in motion. Its invention may be considered as having opened a new era in the history of machines for raising water, for it is susceptible of an almost endless variety of modifications, and of being applied to a great number of purposes. To understand this it is only necessary to bear in mind that the relative position of the two columns is immaterial: they may be a mile distant from each other, or they may be nearly together. The one that raises the other may be above, below, or on a level with the latter; both may be conveyed in pipes along or under the surface of the ground, and in any direction: the only condition required is, that the perpendicular

362

Pressure Engine at Chemnitz.

[Book III. distance between the upper and lower orifices of the pipe in which the motive column flows, shall be equal to the force required to raise the other to the proposed elevation.

A pressure engine on the principle of Heron's fountain, erected by M. Hoell in 1755, to raise water from one of the mines in Hungary, has long been celebrated. In the vicinity of one of the shafts at Chemnitz, there is a hill upon which is a spring of water, one hundred and forty feet above the mouth of the shaft. This spring furnishes more water than that which rises at the bottom of the mine, which is one hundred and four feet below the mouth of the shaft. The water in the mine is raised by means of that on the hill by an apparatus similar to the one figured in the annexed cut. A represents a strong copper vessel eight feet and a half high, five feet diameter, and two inches thick. A large cock marked 3 is inserted near the bottom, and a smaller one 2 near the top. From this vessel a pipe D, two inches in diameter, reaches down and is connected to the top of the vessel B at the bottom of the shaft. This vessel is smaller than the upper one, being six feet and a half high, four feet diameter, and two inches thick, and of the same material as the other. A pipe E, four inches diameter, rises from near the bottom of B to the surface of the ground, where it discharges the water. The pipe C conveys the water from the spring on the hill; it is also four inches diameter, and descends to near the bottom of A. It is furnished with a cock 1. Water is admitted into B through a cock 4, or a valve opening inwards, which closes when B is filled. The vessel A is supposed to be empty, or rather filled with air, and its two cocks shut. The cock 1 is then opened, when the water rushing into A condenses the air within it and the pipe D, and this air pressing on the water in B, forces it up the pipe E. As soon as it ceases to flow through E, the cock 1 is shut and 2 and 3 are opened, when the water in A is discharged at 3. The cock or valve at the bottom of B is opened, and the water entering drives the air up D into A where it escapes at 2. The operation is then repeated as before.

E D

No. 164. Pressure Engine at
Chemnitz.

If, when water ceases to run at E, the cock 2 be opened, both water and air rush out of it together, and with such violence that the liquid is, by the generation of cold consequent on the sudden expansion of the condensed air, converted into hail or pellets of ice. This fact is generally shown to strangers, who are usually invited to hold their hats in front of the cock so as to receive the blast; when the hail issues with such violence, as frequently to pierce the hats, like pistol bullets. This mode of producing ice was known to the marquis of Worcester, who refers to it in the eighteenth proposition of his Century of Inventions, relating to an "artificial fountain, holding great quantity of water, and of force sufficient to make snow, ice, and thunder." Some additions to the machine at Chemnitz, by which it might be rendered self-acting, were proposed in 1796. They consisted of small vessels suspended from levers that were secured

Chap. 9.]

Wirtz's Pump.

363

to the shanks of the cocks, which they opened and shut in the same manner as shown in No. 160. A similar contrivance may be seen in several old authors-it is in the Spiritalia: Decaus, Fludd, Moxon and Switzer have all given figures of it. The quantity of water raised from the shaft compared with that expended from the spring was as 42 to 100.

By arranging a series of vessels above each other and connecting them by pipes as in No. 163, water may be raised to almost any height, in locations that have the advantage of a small fall. The distance between the vessels not exceeding the perpendicular descent of the motive column, which last is made to transmit its force to each vessel in succession-forcing the contents of one into the next above, and so on. Such a machine is interesting as showing the extent to which the principle of Heron's fountain may be applied, but for practical purposes it is of little value. It is too complex (if made self-acting) and too expensive for common use; and it is far inferior to the water ram. It was described by Dr. Darwin, in his Phytologia, to which modern writers generally refer, but it is an old affair. It is figured by Moxon in his "Mechanick Powers," Lon. 1696, and is mentioned by older authors. It is substantially the same as the double fountain of Heron, as found in the Spiritalia and the works of most writers on hydraulics.

By far the most novel and interesting modification of Heron's fountain was devised in the year 1746 by H. A. Wirtz, a Swiss pewterer or tinplate worker of Zurich. It is sometimes named a spiral pump, and was made to raise water for a dye house in the vicinity of that city. What the circumstances were that led Wirtz to its invention we are not informedwhether it was suggested by some incident, or was the result of reasoning alone. It is represented in the illustrations Nos. 165 and 166, the first being a section and the latter an external view.

No. 166. View of Wirtz's Pump.

No. 165. Section of Wirtz's Pump. Wirtz's machine consists either of a helical or a spiral pipe. As the former it is coiled round in one plane as A B C D E F in No. 165. As a spiral it is arranged round the circumference of a cone or cylinder, and then resembles the worm of a still. The interior end at G is united by a water tight joint to the ascending pipe H. See No. 166. The open end

364

Wirtz's Pump.

[Book III. of the coil is enlarged so as to form a scoop. When the machine, immersed in water as represented, is turned in the direction of the arrow, the water in the scoop, as the latter emerges, passes along the pipe driving the air before it into G H, where it escapes. At the next revolution both air and water enter the scoop; the water is driven along the tube as before, but is separated from the first portion by a column of air of nearly equal length. By continuing the motion of the machine another portion of water and another of air will be introduced. The body of water in each coil will have both its ends horizontal, and the included air will be of about its natural density; but as the diameters of the coils diminish towards the centre, the column of water which occupied a semicircle in the outer coil, will occupy more and more of the inner ones as they approach the centre G, till there will be a certain coil, of which it will occupy & complete turn. Hence it will occupy more than the entire space within this coil, and consequently the water will run back over the top of the succeeding coil, into the right hand side of the next one and push the water within it backwards and raise the other end. As soon as the water rises in the pipe G H, the escape of air is prevented when the scoop takes in its next quantity of water. Here, then, are two columns of water acting against each other by hydrostatic pressure, and the intervening column of air. They must compress the air between them, and the water and air columns will now be unequal. This will have a general tendency to keep the whole water back and cause it to be higher on the left or rising side of each coil, than on the other. The excess of height will be just such as produces the compression of the air between that and the preceding column of water. This will go on increasing as the water mounts in H. Now at whatever height the water in H may be, it is evident that the air in the small column next to it will always be compressed with the weight of the water in H-an equal force must therefore be exerted by the water in the coils to support the column in H. This force is the sum of all the differences between the elevation of the inner ends of the water in each coil above the outer ends; and the height to which the water will rise in H will be just equal to this sum. Dr. Gregory observes that the principles on which the theory of this machine depends are confessedly intricate; but when judiciously constructed, it is very powerful and effective in its operation. It has not been ascertained whether the helical or spiral form is best. Some of these machines were erected in Florence in 1778. In 1784, one was made at Archangelsky, that raised a hogshead of water in a minute to an elevation of seventy-four feet, and through a pipe seven hundred and sixty feet long. See Gregory's Mechanics, vol. ii.

It perhaps may facilitate an understanding of this curious machine, by remarking that the pressure exerted by the column of water in one side of each coil is proportioned to its length, and that this pressure is transmitted, through the column of air between them, to that of the next: the combined force of both is then made to act, by the revolution of the tubes, upon the third column, and so on, till the accumulated force of them all is communicated to the water in H; and hence the elevation to which water can be thus raised, can never exceed the sum of the altitudes of the liquid columns in the coils.

END OF THE THIRD BOOK.

BOOK IV.

MACHINES FOR RAISING WATER, (CHIEFLY OF MODERN ORIGIN)
INCLUDING EARLY APPLICATIONS OF STEAM FOR
THAT PURPOSE.

CHAPTER I.

DEVICES of the lower animals-Some animals aware that force is increased by the space through which a body moves-Birds drop shell fish from great elevations to break the shells-Death of Eschylus -Combats between the males of sheep and goats-Military ram of the ancients-Water rams-Waves -Momentum acquired by running water-Examples-Whitehurst's machine-Hydraulic ram of Montgolfier-"Canne hydraulique" and its modifications.

Or the machines appropriated to the fourth division of this work, (see page 8,) centrifugal pumps and a few others have already been described. There remain to be noticed, the water ram, canine hydraulique, and devices for raising water by means of steam and other elastic fluids.

If the various operations of the lower animals were investigated, a thousand devices that are practised by man would be met with, and probably a thousand more of which we yet know nothing. Even the means by which they defend themselves and secure their food or their prey, are calculated to impart useful information. Some live by stratagem, laying concealed till their unsuspecting victims approach within reach-others dig pitfalls to entrap them; and others again fabricate nets to entangle them, and coat the threads with a glutinous substance resembling the birdlime of the fowler. Some species distill poison and slay their victims by infusing it into their blood; while others, relying on their muscular energy, suffocate their prey in their embraces and crush both body and bones into a pulpy mass. The tortoise draws himself into his shell as into a fortress and bids defiance to his foes; and the porcupine erects around his body an array of bayonets from which his enemies retire with dread. The strength of the ox, the buffalo and rhinoceros is in their necks, and which they apply with resistless force to gore and toss their enemies. The elephant by his weight treads his foes to death; and the horse by a kick inflicts a wound that is often as fatal as the bullet of a rifle; the space through which his foot passes, adding force to the blow.

There are numerous proofs of some of the lower animals being aware that the momentum of a moving body is increased by the space through which it falls. Of several species of birds which feed on shell fish, some, when unable to crush the shells with their bills, carry them up in the air, and let them drop that they may be broken by the fall. (The Athenian poet Eschylus, it is said, was killed by a tortoise that an eagle dropped upon his bald head, which the bird, it is supposed, mistook for a stone.)