Book V. LABOURS OF THE SIMPLEST KIND. 507 



at the other, and the weight between them. The weight is carried or moved on by the 

 continual change of the fulcrum with the turning of the wheel; and this turning is 

 produced by the operator throwing forward his centre of gravity so as to push against 

 the wheel by means of the movable axle, &c. The chief obstacles to wheeling are the 

 roughness or softness of the surface to be wheeled on. Where this is firm, there wheel- 

 ing will be best performed with the greater part of the load resting on the axle ; but 

 where soft and deep, the centre of gravity should be nearest the operator, who will find it 

 easier to carry than to overcome excessive friction. Dry weather is obviously preferable 

 for this operation. " With wheelbarrows," Dr. Young observes, " men will do half as 

 much more work as with hods." 



SI 19. All these operations may be varied in quantity, either by a variation in the 

 weight or gravity of the man, or moving power ; or by a variation in the time or rapidity 

 of his motions. Thus a heavy man may, in one movement, lift a weight ten times 

 greater than can be done by one of less weight ; but a light man may, by increasing the 

 time of performance, lift the same weight at ten times. A man, who in digging can 

 apply with his feet five cwt. of his weight towards pushing the wedge or blade of the 

 spade into the soil, has an apparent advantage over a lighter man who can only apply 

 three cwt. of mere gravity for that purpose ; but yet the latter may equal the former, by 

 accompanying his power, or foot, with a proportionate increase of motion. The power 

 in this last case is 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 with 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 Labours of the simplest Kind. 



3120. The manual labours of the field are, next to the general labours enumerated, 

 among the simplest required of the human operator, demanding, in addition to health 

 and strength, but little skill in their performance. 



3121. Breaking stones is an easy labour, requiring very little skill, and no great degree 

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

 at which they can be broken by one blew or more of an iron-headed hammer. In general 

 they are broken on the 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 broken on a table nearly as high as a man's middle, which is now 

 the practice under the direction of the best road-makers. 



3122. 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 pulverising the soil, the most favourable 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. 



3123. 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 unbrDken 

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

 furrow ; 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 

 a uniform depth throughout ; to reverse the position of each spitful, so that 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 as possible, and 

 place it separated or isolated as much as can be effected, where aeration is the ob- 

 ject; to mix in manures regularly, where they are added; to bury weeds not likely 

 to rise again, and to remove others, and all extraneous matters, as stones, &c, in 



