THE PULLEY AND WINDLASS.
In those vast periods preceding the dawn of history, water wasas heavy and as necessaryfor the use of mankind and animals as it is to-day; the toil and labor in securing it must indeed have been hard. Doubtless, the first inventions of the primitive man were first made—perhaps, after weapons of defence—to relieve himself of the painful endeavor of supplying the precious liquid.
There are reasons which render it probable that thesingle pulleywas devised to raise water and earth from wells; the latter are not only of the highest antiquity but they are the only known works of man in early times in which the pulley could have been required or applied. That it preceded the invention of ships and the erection of lofty buildings of stone, is all but certain; but for what purpose, save for raising of water, the pulley could have been previously required it would be difficult to divine; it seems to have been the first addition made to those primitive implements, the cord and the bucket.
By itthe friction of the ropein rubbing against the curb and the consequent loss of a portion of the power expended in raising the water, were avoided, and by it also a beneficialchange in the direction of the powerwas attained; instead of being exerted in an ascending direction, it is applied more conveniently and efficiently in a descending motion as shown in the various figures and illustrations in the preceding pages.
But the grand advantage of the pulley in the early ages was this:—by it the vertical direction in which men exerted their strength, could be directly changed into a horizontal line, by which changeanimals could be employed.
The wells of Asia, frequently varying from two to three, and even four hundred feet in depth, obviously required more than one person to raise the contents of an ordinary sized vessel; and where numbers of people depended on such wells, not merely to supply their domestic wants, but for the purposes of irrigation, the substitution of animals in place of men to raise water, became a matter almost of necessity, and was certainly adopted at a very early period. In employing an ox for this purpose, the simplest way and one which deviated the least from their accustomed method, was merely to attach the end of the rope to the yoke, after passing it over a pulley fixed sufficiently high above the mouth of the well, and then driving the animal a distance equal to its depth, in a direct line from it, when the bucket charged with the liquid would be raised from the bottom.
Although it may never be known to whom the world is indebted for thewindlass, there are circumstances which point to the construction of wells and raising of water from them, as among the first uses to which it as well as the pulley, was applied. The windlass possesses an important advantage over the single pulley in lifting weights, or overcoming any resistance since the intensity of the force transmitted through it can be modified, either by varying the length of the crank, or the circumference of the roller on which the rope is coiled. Sometimes a single vessel and rope, but frequently two, are employed as shown in several of the preceding illustrations; one of these is theChinese Windlass. This furnishes the means of increasing mechanical energy to almost any extent, and as it is used to raise water from some of those prodigiously deep wells already noticed, a figure of it,page 47, has been inserted. The roller consists of two parts of unequal diameters, to the extremities of which the ends of the rope are fastened on opposite sides, so as to wind round both parts in different directions. As the load to be raised is suspended to a pulley, every turn of the roller raises a portion of the rope equal to the circumference of the thicker part, but at the same time lets down a portion equal to that of the smaller; consequently the weight is raised at each turn, through a space equal only to half the difference between the circumferences of the two parts of the roller. The action of this machine is therefore slow, but the mechanical advantages are proportionately great.
Fig. 79.
Fig. 79.
Thefusee windlassis shown in Fig. 79. This is an early invention designed to overcome in a mechanical method the greater weight which the rope hung at its extremity has, as compared to what it is when nearly wound up. At the bottom of the well the rope then being at its heaviest period is wound upon the small end of the fusee; and as the length diminishesit coils round the larger part.(See Fig. 79), which is however inaccurately drawn—as the bucket is at the top of the well; it should have been represented as suspended from the large end of the fusee.
The value of a device like this will be appreciated when the great depth of some wells is considered and the consequent additional weight of the chains. In the fortress of Dresden is a well eighteen hundred feet deep; at Augustburgh is a well in which half an hour is required to raise the bucket; and at Nuremburgh another, sixteen hundred feet deep. In all these, the water is raised by chains, and the weight of the one used in the latter is stated to be upwards of a ton.
Fig. 80.
Fig. 80.
The tympanum and noriain all their modifications have been considered as originating in the gutter orjantu, andthe swape; while the machine we are now to examine is evidently derived from the primitivecord and bucket. The first improvement of the latter was the introduction of a pulley or sheave over which the cord was directed—the next was the addition of another vessel, so as to have one at each end of the rope, and the last and most important consisted in uniting the ends of the rope, and securing to it a number of vessels at equal distances through the whole of its length—and thechain of potswas the result.(See Fig. 80.)
The general construction of this machine will appear from an examination of those which are employed to raise water from Joseph’s well at Cairo, represented onpage 45. Above the mouth of each shaft a vertical wheel is placed, over which two endless ropes passand are suspended from it. These are kept parallel to, and at a short distance from each other, by rungs secured to them at regular intervals, so that when thus united, they form an endless ladder of ropes. The rungs are sometimes of wood, but more frequently of cord like the shrouds of a ship, and the whole is of such a length that the lowest part hangs two or three feet below the surface of the water that is to be raised. Between the rungs, earthenware vases (of the design shown at A A) are secured by cords round the neck, and also round a knob formed on the bottom for that purpose.
Fig. 81.
Fig. 81.
In all the preceding machines the roller is used in ahorizontalposition; but at some unknown period of past ages, another modification was devised, one by which the power could be applied at any distance from the center. Instead of placing the roller as before, over the well’s mouth, it was removed a short distance from it, and secured in a vertical position, by which it was converted into the wheel or capstan. One or more horizontal bars were attached to it, of a length adapted to the power employed, whether of men or animals; and an alternating rotary movement imparted to it, as in the common wheel or capstan, represented in the figure. It appears that machines of this kind, and worked bymenwere common in Europe previous to, and at the time he wrote. Sometimes the shaft was placed in the edge of the well, so that the person who moved it walked round the latter, and thus occupied less space.