Book V. LABORS OF THE SIMPLEST KIND. 451 



13 said to be obtained by the momentum, or quantity of matter in a body multiplied by 

 the velocity with which it is moved. Power, therefore, we thus ascertain, is obtained by 

 matter and motion jointly, and what may be deficient in the one, may be made up by 

 excess in the other. Thus, a small, light workman may (though M'ith more animal 

 exertion,) produce as much work as a larger or heavier man : for if we suppose the 

 quantity of matter in the large man to be thirty, and his motion at the rate of two, then 

 if the quantity of matter in the small man be twenty, and his motion at the rate of three, 

 he will produce an equal effect with the large man. As small human machines, or men, 

 are generally constructed of finer materials, or more healthy and animated, than large 

 ones, the small man performs his rapid motions with nearly as great ease to himself as 

 the heavy man moves his ponderous weight; so that in point of final result they are very 

 nearly on a par. 



Sect. II. Agricultural Labors of the Simplest Kind. 



2884. The manual labors of the field are, next to the general labors enumerated, among 

 the simplest required of the human operator, who, provided he has health and strength, 

 may perform them with very little skill. 



2885. Breaking stones is an easy labor requiring very little skill, and no great degree 

 of strength. The stones are previously reduced in the quarrying, or otherwise, to such 

 sizes as can be broke by one or more blows of an iron headed hammer. In general they 

 are broke on the same plane on which the operator stands, but the blow has more effect 

 when the stone is raised about eighteen inches, and for small stones, the most work will 

 be done when they are broke on a table nearly as high as a man's middle, which is now 

 the practice under the direction of the best road makers. 



2886. Picking. The pick is a blunt wedge, with a lever attached to it nearly at right 

 angles, and the operation of picking consists in driving in the wedge so as to produce 

 fracture, and then causing it to operate as a compound lever by the first lever or handle, 

 so as to effect separation, and thus break up and loosen hard, compact, or stony soils. It 

 is also used to loosen stones or roots ; and the pick-axe is used to cut the latter. For 

 breaking and pulverizing the soil, the most favorable conditions are, that the earth should 

 be moderately moist, to facilitate the entrance of the pick, but in tenacious soils not so 

 much so as to impede fracture and separation. 



2887. Digging. The spade is a thin wedge, with a lever attached in the same plane, 

 and the operation of digging consists in thrusting in the wedge by the momentum (or 

 weight and motion,) of the operator, which effects fracture ; a movement of the lever 

 or handle next effects separation, whilst the operator, by stooping and rising again, lifts 

 up the spitful or section of earth on the blade or wedge of the spade, which, when so 

 raised, is dropped in a reversed position, and at a short distance from the unbroken 

 ground. The separation between the dug and undug ground is called the trench or fur- 

 row ; and when a piece of ground is to be dug, a furrow is first opened at that end of it 

 where the work is to commence, and the earth carried to that end where it is to termi- 

 nate, where it serves to close the furrow. In digging, regard must be had to maintain 

 an uniform depth throughout, to reverse the position of each spitful, so as what was 

 before surface may now be buried; to break and comminute every part where pul- 

 verisation is the leading object ; to preserve each spitful as entire, and place it separated 

 or isolated as much as possible where aeration is the object ; to mix in manures regularly 

 where they are added ; to bui-y weeds not likely to rise again, and to remove others, and 

 all extraneous matters, as stones, &c. in every case. For all these purposes a deep 

 open trench is requisite, and that this may not be diminished in width and depth in the 

 course of the operation, it must never be increased in length. If allowed to become 

 crooked by irregular advances in the digging, it is thus increased in length, and neces- 

 sarily diminished in capacity, unless, indeed, the dug ground is allowed to assume an 

 uneven surface, which is an equally great fault. Digging for pulverisation, and mixing 

 in manures, is best performed in dry weather ; but for the purposes of aeration, a de- 

 gree of moisture and tenacity in the soil is more favorable for laying it up in lumps or 

 entire pieces. The usual length of the blade of the spade is from ten inches to a foot, 

 but as it is always inserted somewhat obliquely, the depth of pulverisation attained by 

 simple digging seldom exceeds nine inches, and in breaking up firm grounds it is seldom 

 so much. 



2888. Shovelling is merely the lifting part of digging, and the shovel being broader 

 than the spade, is used to lift up fragments separated by that implement or the pick. 



2889. Marking xvith the line is an operation preparatory to some others, and consists 

 in stretching and fixing the line or cord along the surface by means of its attached pins 

 or stakes, in the direction or position desired, and cutting a slight continuous notch, 

 mark, or slit in the ground, along its edge with the spade. 



2890. Trenchijig is a mode of pulverising and mixing the soil, or of pulverising and 

 changing its surface, to any greater depth tlian can be done by the spado alone. For 



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