The cabinet of arts, or general instructor in arts, science, trade, practical machinery, the means of preserving human life, and political economy / By Hewson Clarke and John Dougall.

  • Clarke, Hewson, 1787-1832?
Date:
1817
Catalogue details

Licence: Public Domain Mark

Credit: The cabinet of arts, or general instructor in arts, science, trade, practical machinery, the means of preserving human life, and political economy / By Hewson Clarke and John Dougall. Source: Wellcome Collection.

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    ration. The muscles of his neck, back, and loins, keep his body and head in the proper position to sustain the weight: those of his shoul- ders and arms help to keep it in its place ; and those of his thighs and leo-s raise the weight of the whole body and the burthen, as the man walks along. Working in this way, three men will do more than a horse, and two often do as much, as may be seen every day in the la- bour of a London porter. One of these men will carry a load of 200 pounds, and walk at the rate of three miles an hour: a coal-heaver will carry 250 pounds, but then he does not go far with his load.— Chairmen do not act with the same muscles as porters; but as they have straps brought down from their shoulders to the poles of the chair or loaded barrow, the muscles of the back, loins, and legs are all em- ployed. Two chairmen will walk with 300 pounds (150 to each) at the rate of four miles an hour. The most effectual way for a man to exert his strength is in rowing a boat; for there he acts with more muscles than in any other way, besides being assisted by the weight of his body. . Mill-Work. In no manner has the knowledge of mechanic powers been rendered more subservient to the conveniences and comforts of human life than in the construction of mills. To enter into the parti- cular formation of the various kinds of machines in which mill-work is employed, would, in a publication like the present, be impracticable. The following general observations, however, containing the substance of the conclusions, drawn by the most eminent engineers, from theory and experience, will be of use in giving a notion of the pioperties of the most important kind, namely, the corn-mill. Mills are distinguish- ed into various sorts, according to the powers by which they are moved, and the purposes to which they are applied. Such are water-mills, wind-mills, horse-mills, corn-mills, fulling-mills, powder-mills, boring- mills, saw-mills, &c. In ancient times corn was ground oy hand-mills, consisting of two stones, the upper concave, the under convex, like those of water-mills, but much smaller, the upper stone having a handle fixed in it, by which it was turned round. Such were the machines carried along with them by the Roman armies on their expeditions; and such are still to be seen in some of the remote islands of Scotland, where they are called querns. Water-mills are of three sorts, breast % undershot, and overshot-mills, so named from the mode in which the water is applied to the wheel. In the breast-mills the water falls down perpendicularly upon the float-boards or buckets placed round the cir- cumference of the wheel. In the undershot mill, whicli is u$ed where is no fall of water, the stream strikes the float-boards at the lowei part of the wheel. In the overshot-mill the water flow3 over the top of the wheel, and is received hi buckets placed all round it. The water-wheel stands perpendicularly, and is, in the best mills, from eighteen to twenty- four feet in diameter, including the float-boards, (See Agriculture) : the water striking on these boards, forces the wheel round, and gives mo- tion to the mill. The axle or shaft of this wheel, which ought to be very strong, passes through the wall to the inside of the mill-house, where it is firmly supported. On it, within the house, is anothei per- pendicular wheel eight or nine feet in diameter, having cogs all round that work in the upright staves or rounds of a trundle moving non- aontally. This trundle is fixed upon a strong iron axle, called the