Читать книгу Memoir, Correspondence, And Miscellanies, From The Papers Of Thomas Jefferson, Volume 2 - Томас Джефферсон, Thomas Jefferson - Страница 33

TO CHARLES THOMSON.

Paris, December 17,1780.

Dear Sir,

A dislocation of my right wrist has for three months past disabled me from writing, except with my left hand, which was too slow and awkward to be employed often. I begin to have so much use of my wrist as to be able to write, but it is slowly, and in pain. I take the first moment I can, however, to acknowledge the receipt of your letters of April the 6th, July the 8th and 30th. In one of these, you say you have not been able to learn, whether, in the new mills in London, steam is the immediate mover of the machinery, or raises water to move it. It is the immediate mover. The power of this agent, though long known, is but now beginning to be applied to the various purposes of which it is susceptible. You observe, that Whitehurst supposes it to have been the agent, which bursting the earth, threw it up into mountains and vallies. You ask me what I think of this book. I find in it many interesting facts brought together, and many ingenious commentaries on them. But there are great chasms in his facts, and consequently in his reasoning, These he fills up by suppositions, which may be as reasonably denied as granted. A sceptical reader, therefore, like myself, is left in the lurch. I acknowledge, however, he makes more use of fact, than any other writer on a theory of the earth. But I give one answer to all these theorists. That is as follows. They all suppose the earth a created existence. They must suppose a creator then; and that he possessed power and wisdom to a great degree. As he intended the earth for the habitation of animals and vegetables, is it reasonable to suppose, he made two jobs of his creation, that he first made a chaotic lump, and set it into rotatory motion, and then waited the millions of ages necessary to form itself? That when it had done this, he stepped in a second time, to create the animals and plants which were to inhabit it? As the hand of a creator is to be called in, it may as well be called in at one stage of the process as another. We may as well suppose he created the earth at once, nearly in the state in which we see it, fit for the preservation of the beings he placed on it. But it is said, we have a proof that he did not create it in its present solid form, but in a state of fluidity: because its present shape of an oblate spheroid is precisely that, which a fluid mass revolving on its axis would assume.

I suppose, that the same equilibrium between gravity and centrifugal force, which would determine a fluid mass into the form of an oblate spheroid, would determine the wise creator of that mass, if he made it in a solid state, to give it the same spheroidical form. A revolving fluid will continue to change its shape, till it attains that in which its principles of contrary motion are balanced. For if you suppose them not balanced, it will change its form. Now the same balanced form is necessary for the preservation of a revolving solid. The creator, therefore, of a revolving solid, would make it an oblate spheroid, that figure alone admitting a perfect equilibrium. He would make it in that form, for another reason; that is, to prevent a shifting of the axis of rotation. Had he created the earth perfectly spherical, its axis might have been perpetually shifting, by the influence of the other bodies of the system; and by placing the inhabitants of the earth successively under its poles, it might have been depopulated; whereas, being spheroidical, it has but one axis on which it can revolve in equilibrio. Suppose the axis of the earth to shift forty-five degrees; then cut it into one hundred and eighty slices, making every section in the plane of a circle of latitude, perpendicular to the axis: every one of these slices, except the equatorial one, would be unbalanced, as there would be more matter on one side of its axis than on the other. There could be but one diameter drawn through such a slice, which would divide it into two equal parts. On every other possible diameter, the parts would hang unequal. This would produce an irregularity in the diurnal rotation. We may, therefore, conclude it impossible for the poles of the earth to shift, if it was made spheroidical; and that it would be made spheroidical, though solid, to obtain this end. I use this reasoning only on the supposition, that the earth has had a beginning. I am sure I shall read your conjectures on this subject with great pleasure, though I bespeak beforehand, a right to indulge my natural incredulity and scepticism. The pain in which I write, awakens me here from my reverie, and obliges me to conclude with compliments to Mrs. Thomson, and assurances to yourself of the esteem and affection with which I am sincerely, Dear Sir, your friend and servant,

Th: Jefferson.

P. S. Since writing the preceding, I have had a conversation on the subject of the steam-mills, with the famous Boulton, to whom those of London belong, and who is here at this time. He compares the effect of steam with that of horses, in the following manner. Six horses, aided with the most advantageous combination of the mechanical powers hitherto tried, will grind six bushels of flour in an hour; at the end of which time they are all in a foam, and must rest. They can work thus six hours in the twenty-four, grinding thirty-six bushels of flour, which is six to each horse, for the twenty-four hours. His steam-mill in London consumes one hundred and twenty bushels of coal in twenty-four hours, turns ten pair of stones, which grind eight bushels of flour an hour each, which is nineteen hundred and twenty bushels in the twenty-four hours. This makes a peck and a half of coal perform exactly as much as a horse in one day can perform.