HAND-MILLS. This term does not properly apply to any specific kind of mill, but to all that are worked by hand, such as those employed in the domestic offices of grinding coffee, pepper, &c. There are, however, mills of a la r description, which are also worked by hand for grinding malt, wheat, and other substances ; and in the houses for the reception and employment of the poor, it is not uncommon to employ the united force of a great number of persons in grinding corn and dressing the meal for the establishment ; and the mode of applying their power is almost uniformly that of turning a winch or crank, made of sufficient length for that purpose. The winch undoubtedly possesses the advantages of great simplicity and convenience; and it has pro bably, on those accounts, been generally adopted. It has, however, been the opinion of many eminent mechanics, that the most effective mode of employing human force, is the action of rowing a boat. On this point the ingenious Dr. Desaguliers observed, that more muscles are employed at once for over coming the resistance, than in any other position ; and that the weight of his body assists in the act of pulling backwards. The following mechanical arrangement for carrying the principle into effect is given in Brockler 's Theatrum Machinarum. The ver tical shaft e carries a large toothed wheel the latter being intended to operate partly as a regulating fly. Upon the crank a hangs one end of an iron b, the other end of which hangs upon the lever h 1, the motion being per fectly free at both ends of the bar 1. One end of the lever h 1 hangs upon the fixed hook f about which, as a centre of motion, it turns ; then, while a man, by pulling at the lever h I, moves the extremity 1 from 1 to k, the bar b, acting upon the crank a, gives to the wheel a half a rotation ; and the momen tum it has acquired will carry them on, the man at the lever suffering it to turn back from k to 1, while the other half of the rotation of the wheel is completed. In like manner another sufficient pull at the lever h 1 gives another rotation to the wheel c, and so on at pleasure. The wheel c turns by its teeth the trundle d, the spindle of which carries the upper mill-stone. If the number of the teeth in the wheel c be six times the number of the cogs in the trundle d, then the labourer, by making ten pulls at the lever h I in a minute, will give sixty revolutions to the upper mill-stone in the same space of time.
We have given insertion to this "rowing-mill," as it is termed, on account of the great praise bestowed upon it by succeeding eminent writers; but we cannot regard it as a very judicious mode of carrying the principle into effect, for two reasons ;—Fsret, the large wheel making but ten revolutions per minute, will not become a very efficient regulator of power ; if fixed upon the first motion, it must be made inconveniently large or weighty to collect the requisite force to be useful. If a fiy-wheel be used at all, it should be put on the axis
of the trundle d, where the velocity is six times greater ; the increased momentum it would here acquire, would far more than compensate for the small loss of effect by its removal farther from the motive force. But we doubt much the use of a fly-wheel at all in the present case, because a heavy mill stone is put into operation ; and that is, in effect, a far more efficacious fly wheel than the above described. Second, because we think the inventor has imitated the defects as well as the advantages of the rowing action. In this mill the workman is supposed to pull the lever h I through the arc of a circle 1 k; and this indirect action, it will be noticed, is performed in a horizontal plane, by which a contortion of the man's body results that must be unfavour able to his health, and the most efficient exercise of his strength. To avoid these defects in the rowing-mill, we propose the following simplified, and, we trust, improved arrangement. a represents a seat for one or two men ; b a board to press their feet against in pulling back by the cross handle c, which is connected to a rod d that slides straight through brasses fixed in a standard e ; at f is a hinge joint, which permits the connecting rod g to vibrate with the revolution of the crank Is, whose axis actuates the wheel i, the pinion or trundle j, on the axis k of which, is fixed the runner-stone 1, serving azo the office of a fly-wheeL In applying the labour of more men to an apparatus of this kind, there would be some advantage in placing them opposite to each other, so that a pull should be made each way. For this purpose the rod d d might be lengthened, another seat be placed on the other side of the standard e and another cross handle between d and f ; the men sitting here on each aide of the rod d.
Having now explained what is deemed the most advantageous application of manual labour to mills, and the undefined nature of the term which heads this article, we refer the reader for more information on the subject, and that of mills generally, to the article MILL.