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true philosophy; for the illumination of the understanding, the extracting of axioms, and the producing of many noble works and effects. For he hopeth by this means to acquit himself of that for which he taketh himself in a sort bound, and that is, the advancement of all learning and sciences. For, having in this present work collected the materials for the building, and in his Novuma Organum (of which his lordship is yet to publish a second part) set down the instruments and directions for the work; men shall now be wanting to themselves, if they raise not knowledge to that perfection whereof the nature of mortal men is capable. And in this behalf, I have heard his lordship speak complainingly, that his lordship (who thinketh he deserveth to be an architect in this building) should be forced to be a workman and a labourer, and to dig the clay and burn the brick; and more than that, (according to the hard condition of the Israelites at the latter end) to gather the straw and stubble over all the fields to burn the bricks withal. For he knoweth, that except he do it, nothing will be done: men are so set to despise the means of their own good. And as for the baseness of many of the experiments; as long as they be God's works, they are honourable enough. And for the vulgarness of them, true axioms must be drawn from plain experience and not from doubtful; and his lordship's course is to make wonders plain, and not plain things wonders; and that experience likewise must be broken and grinded, and not whole, or as it groweth. And for use; his lordship hath often in his mouth the two kinds of experiments, experimenta fructifera and experimenta lucifera: experiments of Use, and experiments of Light: and he reporteth himself, whether he were not a strange man, that should think that light hath no use, because it hath no matter. Further, his lordship thought good also to add unto many of the experiments themselves some gloss of the causes: that in the succeeding work of interpreting nature and framing axioms, all things may be in more readiness. And for the causes herein by him assigned; his lordship persuadeth himself, they are far more certain than those that are rendered by others; not for any excellency of his own wit (as his lordship is wont to say), but in respect of his continual conversation with nature and experience. He did consider likewise, that by this addition of causes, men's minds (which make so much haste to find out the causes of
things) would not think themselves utterly lost in a vast wood of experience, but stay upon these causes (such as they are) a little, till true axioms may be more fully discovered. I have heard his lordship say also, that one great reason why he would not put these particulars into any exact method (though he that looketh attentively into them shall find that they have a secret order) was because he conceived that other men would now think that they could do the like, and so go on with a further collection; which, if the method had been exact, many would have despaired to attain by imitation. As for his lordship's love of order, I can refer any man to his lordship's Latin book, De Augmentis Scientiarum; which (if my judgment be anything) is written in the exactest order that I know any writing to be. I will conclude with an usual speech of his lordship's; That this work of his Natural History is the world as God made it, and not as men have made it; for that it hath nothing of imagination.
This epistle is the same that should have been prefixed to this book if his lordship had lived.
Experiments in consort touching the straining and passing of bodies one through another; which they call Percolation.
1. DIG a pit upon the sea-shore, somewhat above the high-water mark, and sink it as deep as the low-water mark; and as the tide cometh in, it will fill with water, fresh and potable. This is commonly practised upon the coast of Barbary, where other fresh water is wanting. And Cæsar knew this well when he was besieged in Alexandria: for by digging of pits in the seashore, he did frustrate the laborious works of the enemies, which had turned the sea-water upon the wells of Alexandria; and so saved his army, being then in desperation.' But Cæsar mistook the cause, for he thought that all sea-sands had natural springs of fresh water. But it is plain that it is the sea-water; because the pit filleth according to the measure of the tide 2; and the sea-water passing or straining through the sands leaveth the saltness.
2. I remember to have read that trial hath been made of salt water passed through earth, through ten vessels one within another, and yet it hath not lost his saltness, as to become potable: but the same man saith, that (by the relation of another) salt water drained through twenty vessels hath become fresh. This experiment seemeth to cross that other of pits
1 Hirtius, De Bello Alexandrino, c. 8. and 9. ; and see Aristot. Prob. sect. xxiii. 21. and 37.
2 Wells of fresh water close upon the sea shore sometimes ebb and flow with the tide. But this arises from the comparative levity of the fresh water, in consequence of which it is, so to speak, floated up when the tide comes in. Or it may arise from the presence of compressed air in the interstices of the soil which lies between the fresh and the salt water; an explanation which appears to be confirmed by recent experiments on the subject of drainage.
3 This statement is taken from J. B. Porta. See his Natural Magic, xx. 1. Aristotle, in support of the opinion that fish are nourished by the fresh water present in the sea, states that a closed vessel of thin wax immersed for a certain time in the sea
made by the sea-side; and yet but in part, if it be true that twenty repetitions do the effect. But it is worth the note, how poor the imitations of nature are in common course of experiments, except they be led by great judgment, and some good light of axioms. For first, there is no small difference between a passage of water through twenty small vessels, and through such a distance as between the low-water and high-water mark. Secondly, there is a great difference between earth and sand; for all earth hath in it a kind of nitrous salt, from which sand is more free; and besides earth doth not strain the water so finely as sand doth. But there is a third point that I suspect as much or more than the other two; and that is, that in the experiment of transmission of the sea-water into the pits the water riseth; but in the experiment of transmission of the water through the vessels it falleth. Now, certain it is that the salter part of water (once salted throughout) goeth to the bottom. And therefore no marvel if the draining of water by descent doth not make it fresh. Besides, I do somewhat doubt that the very dashing of the water that cometh from the sea is more proper to strike off the salt part, than where the water slideth of her own motion.
3. It seemeth percolation, or transmission, (which is commonly called straining) is a good kind of separation; not only of thick from thin, and gross from fine, but of more subtile natures; and varieth according to the body through which the transmission is made as if through a woollen bag, the liquor leaveth the fatness; if through sand, the saltness, &c. They speak of severing wine from water, passing it through ivy wood, or through other the like porous body; but non constat.'
4. The gum of trees (which we see to be commonly shining and clear) is but a fine passage or straining of the juice of the tree through the wood and bark. And in like manner, Cornish diamonds and rock rubies (which are yet more resplendent than gums) are the fine exudations of stone.
5. Aristotle giveth the cause, vainly, why the feathers of birds are of more lively colours than the hairs of beasts; for no beast hath any fine azure, or carnation, or green hair. He saith, it is because birds are more in the beams of the sun than
is found to contain fresh water. If this is true, the explanation probably is, that the temperature of the sea at the depth to which the vessel is sunk happens to be below the dew point of the air at the surface.
1 Pliny, xvi. 63.; and Cato, De Re Rusticâ, cxi.