MANUFACTURES.

3

Manu-

factures.

lbs.

6. To drag it by these rollers over a wooden floor required. 28 • Sect. I-

7. When the stone was mounted on a wooden platform, and the same rollers placed between "V"'*

that and a plank floor, it required . 22

From this experiment it results, that the force necessary to move a stone along thesmoothed floor of its quarry is nearly two-thirds of its weight; to move it along a woodenfloor, three-fifths; by wood upon wood, five-ninths ; if the wooden surfaces are soaped,one-sixth; if rollers are used on the floor of the quarry, it requires one thirty-secondpart of the weight; if they roll over wood, one-fortieth; and if they roll betweenwood, one-fiftieth of its weight.

At each increase of knowledge, as well as on the contrivance of every new Tool, humanlabour becomes abridged. The man who contrived rollers, invented a Tool by whichhis power was quintupled. The workman who first suggested the employment of soap,or grease, was immediately enabled to move, without exerting a greater effort, more thanthree times the weight he could before. So sensible are the effects of grease in dimi-nishing friction, that the drivers of sledges in Amsterdam , on which heavy goods aretransported, carry in their hand a rope soaked in tallow, which they throw down fromtime to time before the sledge, in order that by passing over the rope it may becomegreased.

2. The next use of Machinery and Manufactures is —the economy which they produceof human time. So extensive and important is this effect, that we might, if we wereinclined to generalize, embrace almost all their advantages under this one head; but theelucidation of principles of less extent will contribute more readily to a knowledge ofthe subject, and as numerous examples will be presented to the reader in the ensuingpages, we shall restrict our illustrations upon this point.

The Art of using the diamond for cutting glass has undergone, within a few years, a Cutting

. • 00 .... glass with

very important improvement. A glazier’s apprentice, when using a diamond set in athedia-conical ferrule, as was always the practice about twelve years since, found great diffi-culty in acquiring the Art of employing it with certainty, and at the end of a seven years’apprenticeship. many were found but indifferently skilled in its use. This arose fromthe difficulty of finding the precise angle at which the diamond cut, and of guiding italong the glass at the proper inclination when that angle was found. Almost the wholeof the time consumed, and of the glass destroyed in acquiring the Art of cutting glass,may now be saved by the use of an improved tool. The gem is set in a small piece ofsquared brass, with its edge nearly parallel to one side. A person skilled in its usenow files away one side of the brass, until, by trial, he finds that it will act well, whenguided, by keeping this edge pressed against a ruler. The diamond and its mountingare now attached to a stick similar to a pencil, by means of a swivel allowing a smallangular motion. Thus the merest tyro, using it in this form, at once applies it at theproper angle, by pressing the side against a ruler ; and even though the part he holdsin his hand should deviate a little from its proper angle, it communicates no irregularityto the position of the diamond, which rarely fails to do its office when thus employed.

As another example of the economy of time, the use of gunpowder in blasting

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