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have some wash or something to make their teeth better and stronger ? Coral is in use as an help to the teeth of children.

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Experiments in consort touching the generation and

bearing of living creatures in the womb. 758. Some living creatures generate but at certain seasons of the year; as deer, sheep, wild coneys, &c., and most sorts of birds and fishes : others at any time of the year; as men, and all domestic creatures, as horses, hogs, dogs, cats, &c. The cause of generation at all seasons seemeth to be fulness: for generation is from redundance. This fulness ariseth from two causes : either from the nature of the creature, if it be hot and moist and sanguine; or from plenty of food.

For the first, men, horses, dogs, &c. which breed at all seasons, are full of heat and moisture; doves are the fullest of heat and moisture amongst birds, and therefore breed often; the tame dove almost continually. But deer are a melancholy dry creature, as appeareth by their fearfulness, and the hardness of their flesh. Sheep are a cold creature, as appeareth, by their mildness, and for that they seldom drink. Most sort of birds are of a dry substance in comparison of beasts. Fishes are cold. For the second cause, fulness of food; men, kine, swine, dogs, &c. feed full'; and we see that those creatures which being wild generate seldom, being tame generate often; which is from warmth, and fulness of food. We find that the time of going to rut of deer is in September; for that they need the whole summer's feed and grass, to make them fit for generation. And

1 Arist. Prob. x. 49.

or

if rain come early about the middle of September, they go to rut somewhat the sooner; if drought, somewhat the later. So sheep, in respect of their sınall heat, generate about the same time, or somewhat before. But for the most part, creatures that generate at certain seasons, generate in the spring; as birds and fishes; for that the end of the winter, and the heat and comfort of the spring, prepareth them. There is also another reason why some creatures generate at certain seasons; and that is the relation of their time of bearing to the time of generation ; for no creature goeth to generate whilst the female is full ; nor whilst she is busy in sitting, or rearing her young. And therefore it is found by experience, that if you take the

eggs young ones out of the nests of birds, they will fall to generate again, three or four times, one after another.

759. Of living creatures, some are longer time in the womb, and some shorter. Women go commonly nine months; the cow and the ewe about six months; 1 does go about nine months; mares eleven months ; X bitches nine weeks; elephants are said to go two years ; for the received tradition of ten years is fabulous. For birds there is double inquiry: the distance between the treading or coupling, and the laying of the egg; and again, between the egg laid, and the disclosing or hatching: and amongst birds there is less diversity of time than amongst other creatures; yet some there is; for the hen sitteth but three weeks; the turkey-hen, goose, and duck, a month : Quære of others.2 The

1 These statements are very inaccurate. Tessier assigns 282 days in the former case, and 151 in the latter, as mean periods. See Mém. de l'Ac. des Sciences, (1817).

2 The pigeon sits about eighteen days, the swan about thirty-three. The

cause of the great difference of times amongst living creatures, is either from the nature of the kind, or from the constitution of the womb. For the former, those that are longer in coming to their maturity or growth are longer in the womb; as is chiefly seen in men: and so elephants, which are long in the womb, are long time in coming to their full growth. But in most other kinds, the constitution of the womb (that is, the hardness or dryness thereof,) is concurrent with the former cause. For the colt hath about four years of growth; and so the fawn; and so the calf. But whelps, which come to their growth (commonly) within three quarters of a year, are but nine weeks in the womb. As for birds, as there is less diversity amongst them in the time of their bringing forth, so there is less diversity in the time of their growth; most of them coming to their growth within a twelvemonth.

760. Some creatures bring forth many young ones at a burthen: as bitches, hares, coneys, &c. Some (ordinarily) but one; as women, lionesses, &c. This may be caused, either by the quantity of sperm required to the producing one of that kind; which if less be required, may admit greater number; if more, fewer: or by the partitions and cells of the womb, which may sever the sperm.

Experiments in consort touching species visible. 761. There is no doubt but light by refraction will shew greater, as well as things coloured. For like as a shilling in the bottom of the water will shew greater; so will a candle in a lanthorn, in the bottom of the water. I have heard of a practice, that glow-worms in glasses were put in the water to make the fish come. But I am not yet informed whether when a diver diveth, having his eyes open, and swimmeth upon his Isack; whether (I say) he seeth things in the air greater or less. For it is manifest that when the eye standeth in the finer medium, and the object is in the grosser, things shew greater; but contrariwise, when the eye is placed in the grosser medium, and the object in the finer, how it worketh I know not.

turkey-hen about twenty-seven, the duck and goose thirty to thirty-two days. The hen, as Bacon says, about three weeks. See Tessier and F. Cuvier, ubi supra.

1 Arist. Prob. x. 16.

762. It would be well bolted out, whether great refractions may not be made upon reflexions, as well as upon direct beams. For example, we see that, take an empty bason, put an angel of gold, or what you will, into it; then go so far from the bason, till you cannot see the angel, because it is not in a right line; then fill the bason with water; and you shall see it out of his place, because of the reflexion. To proceed therefore, put a looking-glass into a bason of water; I suppose you shall not see the image in a right line, or at equal angles, but aside. I know not whether this experiment may not be extended so as you might see the image, and not the glass; which for beauty and strangeness were a fine proof: for then you should see the image like a spirit in the air. As for example, if there be a cistern or pool of water, you shall place over against it a picture of the devil, or what you will, so as you do not see the water. Then put a lookingglass in the water: now if you can see the devil's picture aside, not seeing the water, it will look like a devil indeed. They have an old tale in Oxford, that

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Friar Bacon walked between two steeples: which was thought to be done by glasses, when he walked upon the ground.

Experiments in consort touching impulsion and per

cussion. 763. A weighty body put into motion is more easily impelled, than at first when it resteth. The cause is partly because motion doth discuss the torpor of solid bodies; which, beside their motion of gravity, have in them a natural appetite not to move at all; and partly because a body that resteth doth get, by the resistance of the body upon which it resteth, a stronger compression of parts than it hath of itself: and therefore needeth more force to be put in motion. For if a weighty body be pensile, and hang but by a thread, the percussion will make an impulsion very near as easily as if it were already in motion.

764. A body over-great or over-small, will not be thrown so far as a body of a middle size : 2 so that it seemeth) there must be a commensuration or proportion between the body moved and the force, to make it move well. The cause is, because to the impulsion there is requisite the force of the body that movetli, and the resistance of the body that is moved : and if the body be too great, it yieldeth too little; and if it be too small, it resisteth too little.

765. It is common experience, that no weight will press or cut so strong, being laid upon a body, as falling or strucken from above. It may be the air hath some part in furthering the percussion ; but the chief cause I take to be, for that the parts of the body

1 Arist. Mech. Quæst. 32.

2 Id. ib. 35.

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