THE HYDRAULIC RAM. 



357 



for watoriiig his poultry, his stock, his dairy and 

 his garden, and for a thousand uses tliat would 

 suggest themselves, were tlie water at hand ? 



Of the machines appropriated to the fourth 

 division of this work, centrifugal pumps and a 

 few others have already been described. There 

 remain to be noticed, the water ram, canne hy- 

 drauiiqne, 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 

 practiced by man would be met with, and prob- 

 ably a thousand more of which we yet know 

 nothing. Even the means by which they de- 

 feud themselves and secure their food or their 

 prey, are calculated to impart useful informa- 

 tion. Some live by stratagem, laying concealed 

 till their unsuspecting victims approach within 

 reach — others dig pitfalls to entrap them ; and 

 otliers again fabricate nets to entangle them, 

 and coat the threads with a glutinous substance 

 resembling the bird-lime of the fowler. Some 

 species distill poison and slay iheir victims by 

 infusing it into their blood ; while others, rely- 

 ing on their muscular energy, suffocate their 

 prey in their embraces and crush both body 

 and bones into a pulpy mass. The tortoise 

 draws liimself 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 wliicli his enemies retire with drIRid. The 

 strength of the ox, the buffalo and rhinoceros is 

 in tiieir necks, and which they apply witli re- 

 sistless 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 

 lorce 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 un- 

 able 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 

 ./Eschuylus, it is i-aid, was killed by a tortoise 

 that an eagle dropped upon his bald head, 

 which the bird, it is supposed, mistook for a 

 stone.) When the males of sheep or goats pre- 

 pare to butt, they always recede backwards to 

 some distance ; and then rushing impetuously 

 forward, (accumulating force as tliey go,) bring 

 their foreheads in contact witii a shock that 

 sometimes proves fatal to both. The ancients, 

 perhaps, from -witnessing the battles of these 

 animals, constructed military engines to act on 

 the same principle. A ponderous beam was 

 suspended at the middle by chains, and one end 

 impelled, by the united efforts of a number of 

 men at the oppo.sitc end, against walls which It 

 demolislieci with slow but sure effect. The bat- 

 tering end was generally, and with the Greeks 

 and Romans uniformly, protected by an iron or 

 hroikze cap in tiie form of a ram's head ; and 

 the entire inslnimenl was named after that ani- 

 mal. It was the most destructive of all their war 

 machinery — no building, however solid, could 

 long withstand its attacks. Plutarch, in his life 

 of Anthony, mentions one eight 1/ feci in length. 



The action of the ram is familiar to most 

 people, but it may not be known to all that sim- 

 ilar results might be produced by a lii)uid as by 

 a solid — that a long commn of water movinij 



with great velocity might be made equally de- 

 structive as a beam of wood or iron — yet so' it is. 

 Waves of the sea act as water-rams against 

 rocks or other bamers that impede their pro- 

 gress, and when their force is increased by 

 storms of wind, the most solid structures give 

 way before them. The old light-house on the 

 Eddystone rocks was thus battered down du- 

 ring a storm in 1703, when the engineer, Mr. 

 Winstanley, and all his people perished. 



The increased force which water acquires 

 when its motion is accelerated, might be shown 

 by a thousand examples : a bank or trough that 

 easily retains it when at rest, or when slightly 

 moved, is often insuflicient when its velocity is 

 greatly increased. When the deep lock of a 

 canal is opened to transfer a boat or a .ship to a 

 lower level, the water is permitted to descend 

 by slow degrees : Avere the gates opened at 

 once, the rushing mass would sweep the gates 

 be'ow before it, or the greater portion would be 

 carried in die .surge quite over them — and per- 

 haps the vessel also. A sluggish stream drops 

 almost perpendicularly over a precipice, but the 

 momentum of a rapid one shoots it over, and 

 leaves, as at Niagara, a wide space between. — 

 It is the same with a stream issuing from a hor- 

 izontal tube — if the liquid pass slowly through, 

 it falls inertly at the orifice, but if its velocity be 

 considerable, the jet is can-led to a distance ere 

 it touches the ground. The level of a great part 

 of Holland is tielow the surface of the sea, and 

 the dykes are in some parts thirty feet high ; 

 v^hcnever a leak occurs, the greatest efforts are 

 made to repair it immediately, and lor the obvi- 

 ous reason that the aperture keeps enlarging 

 and the liquid mass behind is put in motion 

 towards it ; thus the pressure is increased and, 

 if the leak be not stopped, keeps increasing till 

 it bears with irresistible force all obstructions 

 away. A fatal example is recorded in the an- 

 cient history of Holland: — An ignorajit burgher, 

 near Dort, to be revenged on a neighbor, dug 

 a hole through the dyke opposite the house of 

 the latter, unending to clo.se it after his neigh- 

 bor's property had been destroj-ed ; but the 

 water rushed through with an accelerating 

 force, till all resistance was vain, and the whole 

 country became deluged. The ancients were 

 well aware of this accumulation of force in 

 running waters. Allusions to it are very com- 

 mon among the oldest writers, and various max- 

 ims of life were drawn from it. The beginning 

 of strife, says Solomon, '• is as when one let- 

 teth out water" — the '-breach of waters" — 

 " breaking forth of waters " — " ru.shing of mighty 

 waters," &c. are frequently mentioned, to indi- 

 cate the irresistible influence of desolating evils 

 when once admitted. 



That the force which a running stream thus ac- 

 quires may be made to drive a portion of the 

 liquid far above the source whence it flows, is 

 obvious froVn several operations in nature. — 

 During a storm of wind, long swelling waves 

 in the open sea alternately rise and fall, without 

 the crests or tops of any being elevated much 

 above those of the rest ; but when they meet 

 from opposite directions, or w-hen their progress 

 is suddenly arrested by the bow of a ship, by 

 rocks, or other ob.stacles, part of the water is 

 driven to greater elevations. There is a fine 

 example of tiiis at the Eddystone rocks — the 

 heavy swells from the Bay of Bi.scay and from 

 the Ailantic, roll in and break with inconceiva- 

 ble fury upon them, so that volumes of water 

 are thrown up with terrific violence, and tlie 



