« 前へ次へ »
external parts are composed; and the opacity of this nucleus varies in different comets. On its first appearance, and again when it recedes, the luminous part of the comet is faint, and does not extend far from the nucleus; but, as it moves on towards the perihelion, the brightness increases, and the luminous matter lengthens into a train, which, in some cases, has extended across a fourth of the entire circumference of the heavens. But, though the general fact of the increased brightness of comets, and length of their tails, with their approach to the sun, and the consequent inclination of their motion, has been established, the observations have not been uniform or minute enough for proving what proportion the increase of brightness bears to the increase of the velocity, and the diminution of the distance from the sun. No doubt all the comets of which there are wellauthenticated accounts, of great brightness and length of tail, have passed near the sun in their perihelion. Thus the comet of 1769, which was not a fifth of the earth's perihelion distance from the sun, had a tail of 60° in length, as seen at Paris ; while that of 1759, which was more than half the earth's perihelion distance distant, had a train of only 2° or 3°. The length of the tail varies, however, not only with the time at which it is observed, but with the place of observation; - a difference probably depending on the difference of clearness and purity in the air. The tail of the comet of 1759 was 25° long, as measured at Montpelier in the south of France, and considerably more than that, as measured at the Isle of Bourbon, in the Indian Ocean. That of 1769 was 60° at Paris, 70° at Boulogne, 90° between Teneriffe and Cadiz, and 97o at Bourbon. Generally speaking, they appear to be brighter and larger when seen at sea than on land, and in the warmer regions more than in those nearer the poles.
When the superstitious fear of comets, as portending harm to the inhabitants of the earth, had vanished before the light of philosophy, that light was in some danger of giving rise to fear of another sort, fear of physical harm to the earth itself, by the collision of some comet that might cross its path. We have no evidence, however, that such a collision ever did happen, either with the earth or with any other planet; and we have not absolutely correct means of so calculating the place of a comet as to be able to say with certainty that, on a given day, during a given month, or even during a given year, it shall cross the orbit of a planet. The motion of the earth in its orbit is, in round numbers, more than a million and half of miles in a day; and as Clairault, with all his care, did not come nearer the truth than nineteen days, though the collision of a comet and the earth should be calculated from any known data, the earth might in fact be, at the time, far enough from the comet.
Indeed, though the fact of the return of two comets be established, namely, Halley's and Encke's, and the return of every one, if not affected
by physical causes that lie beyond the limits of our present knowledge, bas been rendered exceedingly probable; yet we can observe them for so short a portion of their courses, and these seem so very apt to be altered, that we ought not to speak of them with anything like the certainty with which we speak of the planets. As far as we have been able to examine them, they appear to obey the same laws as the other distinct masses that make up the known part of the system of the universe. Beyond this we know nothing of their nature; and as for their effects, moral or physical, we need give ourselves no trouble about them, for there is not a trace of the existence of such effects upon any authentic record.
MISCELLANEOUS DIRECTIONS, HINTS, AND REMARKS.
XIV. WASHINGTON'S AGRICULTURAL NOTES.
NOTWITHSTANDING the numerous public avocations and duties, in which Washington was engaged for a large portion of his life, it is known, that to no one object did he give so much of his time and attention as to Agricul. ture. The frequency and minuteness of his directions to his managers on this head, and the unceasing correspondence, which he kept up during his absence from Mount Vernon, are truly astonishing, when it is considered in what important and absorbing interests his mind was perpetually occupied. We have selected a few particulars from his manuscript papers, which, at the same time they illustrate his agricultural habits, may in part serve as practical hints, or salutary maxims, to farmers in general.
1. DIRECTIONS TO THE MANAGER OF HIS FARMS.
A system closely pursued, although it may not in all its parts be the best that could be devised, is attended with innumerable advantages. The conductor of the business, in this case, can never be under any dilemma in his proceedings. The overseers, and even the laborers, know what is to be done, and what they are capable of doing, in ordinary seasons. The force to be employed may be in due proportion to the work which is to be performed, and a reasonable and tolerably accurate estimate may be made of the product. But when no plan is fixed, when directions flow from day to day, the business becomes a mere chaos, frequently shifting, and sometimes at a stand, for want of knowing what to do, or the manner of doing it. Thus is occasioned a waste of time, which is of more importance, than is generally imagined.
Nothing can so effectually obviate the evil, as an established system, made known to all who are actors in it, that all may be enabled thereby to do their parts to advantage. This gives ease to the principal conductor of the business, and is more satisfactory to the persons who immediately overlook it, less harassing to the laborers, as well as more beneficial to the employer.
Under this view of the subject, the principal service, which you can render me, is to explain to the overseers (who will be furnished with duplicates) the plan, in all its parts, which is hereafter detailed; to hear their ideas with respect to the order in which the different sorts of work therein pointed out shall succeed each other, for the purpose of carrying it on to the best advantage; to correct any erroneous projects they may be disposed to adopt; and then to see that they adhere strictly to whatever may be resolved on, and that they are always (except when otherwise permitted) on their farms, and with their people. The work, under such circumstances, will go on smoothly; and, that the stock may be well fed, littered, and taken care of according to the directions, it will be necessary to inspect the conduct of the overseers in this particular, and those also whose immediate business it is to attend upon them, with a watchful eye; otherwise, and generally in severe weather, when attention and care are most needed, they will be most neglected.
Economy in all things is as commendable in the manager, as it is beneficial and desirable to the employer ; and, on a farm, it shows itself in nothing more evidently, or more essentially, than in not suffering the provender to be wasted, but, on the contrary, in taking care, that every atom of it be used to the best advantage; and, likewise, in not permitting the ploughs, harness, and other implements of husbandry, and the gears belonging to them, to be unnecessarily exposed, trodden under foot, run over by carts, and abused in otheț respects, More good is derived from attending to the minutiæ of a farm, than strikes people at first view; and examining the farın-yards, fences, and looking into the fields to see that nothing is there but what is allowed to be there, is oftentimes the means of producing more good, or at least of avoiding more evil, than can be accomplished by riding from one working party, or one overseer, to another. I have mentioned these things not only because they have occurred to me, but because, although apparently trifles, they prove far otherwise in the result.
To request that my people may be at their work as soon as it is light, work till it is dark, and be diligent while they are at it, can hardly be necessary, because the propriety of it must strike every manager, who attends to my interest, or regards his own character, and who, on reflecting, must be convinced that lost labor is never to be regained. The presumption is, that every laborer does as much in twenty-four hours as his strength, without endangering his health or constitution, will allow. But there is much more in what is called head work, that is, in the manner of conducting business, than is generally imagined. For take two managers, and give to each the same number of laborers, and let the laborers be equal in all respects. Let both these managers rise equally early, go equally late to rest, be equally active, sober, and industrious, and yet, in the course of the year, one of them, without pushing the hands under him more than the other, shall have performed infinitely more work. To what is this owing? Why, simply to contrivance, resulting from that forethought and arrangement, which will guard against the misapplication of labor, and doing it unseasonably. In ploughing, for instance, though the field first intended for it, or in which the ploughs may actually have been at work, should, from its situation, be rendered unfit (by rain or other cause) to be worked, ond other spots, even though the call for them may not be so urgent, can be ploughed, this business ought to go on, because the general operation is promoted by it. So with respect to other things, and particularly carting, where nothing is more common, than, when loads are to go to a place, and others to be brought from it, though not equally necessary at the same moment, to make two trips, when one would serve. These things are only mentioned to show, that the manager, who takes a comprehensive view of his business, will throw no
For these reasons it is, that I have endeavoured to give a general view of my plans, as to the business of the year, that the concerns of the several plantations may go on without application daily for orders, unless it be in particular cases, or where these directions are not clearly understood.