An entire body of philosophy according to the principles of the famous Renate Des Cartes in three books, (I) the institution ... (II) the history of nature ... (III) a dissertation of the want of sense and knowledge in brute animals ... / written originally in Latin by the learned Anthony Le Grand ; now carefully translated from the last corrections, alterations, and large additions of the author, never yet published ... by Richard Blome.

CHAP. IV. What is the Cause of that Hardness, which is observ'd on the outside of living Bodies.

I. Whence the Hardness of the Surface of Living Bodies doth pro∣ceed. THe Hardness of Bodies consists chiefly in this, that they resist the Touch, and that their parts are not easily separable from each other. And forasmuch as this Resistance to the Touch is perceiv'd on the outside of Living Bodies; it will be worth our enquiry, What might be the Cause of it, that when their Inward substance is so soft, their outside should be hard. Whereof no other Cause seems assignable, but this, That the Outward parts of Living Bodies, are expos'd to the continual impulse of other Bodies. For it is certain, that the Heavenly matter (under which Name we do not only comprehend the Matter of the first and second Element, but also the Air, with the Par∣ticles of the third Element that are mix'd with it) carries the Earth round; and forasmuch as all these Small Bodies cannot pass through the Earth, or any of the Bodies which belong to it, it cannot be otherwise, but that vast numbers of them must dash against Living Bodies, and by their continual beating upon them, render them hard. For by this impulse, their Outward parts are driven closer together, and so become more Compact and Hard.

II. Wherein the Hard∣ness of any Bodies doth consist. For to speak properly, the Hardness of Bodies is nothing else, but the Rest of many Essential or Integral parts, caused by the Pression of the Air, or of the Subtil matter; which acting only on the outside, doth so much drive those Particles inwards, that they can no more be separated, without a perception of some Resistance. For tho' the Subtil matter doth penetrate all Bodies; yet we are to consider, that the Parts of many Bodies are so great and irregular, that they are able to resist its Action and continue at Rest, and by this means constitute Hard Bodies; because they resist or oppose their being divided, and are outwardly so comprest by the Air and the Subtil matter, that it is oftentimes more easie to move them altogether, than to separate them from one another.

III. Whence the Covers of some Li∣ving Bo∣dies do proceed. This is the Cause of those Coverings, which do invest some Living Bodies; as we find that Acorns have Cups; Nuts have Shells; Beans and Pease, Pods; and Trees, Barks: So likewise Fish have Scales, and some of them hard and stony Shells; as Oysters, Crabs, Lobsters, &c. All which without doubt are formed, by the continual impulse of outward Bodies; much in like manner as we find, that the Palms of the Hands of Delvers and Ditchers, by continual handling of the Spade, grow very hard; and as the Soles of our Feet become brawny and thick Skin'd, by assiduous beating against the Ground.

IV. The same is the Cause of the Hardness in Inani∣mate Bo∣dies. They are the same Causes also that produce Hardness in Inanimate Bodies. For Snow laid near the Fire becomes harder and more compact; and the outside of Bread becomes hardned to a Crust; and so likewise the outside of Flesh roasted, broiled, or fryed, grows harder than the in••ide. Neither can any other Reason be given, why Broath, Boil'd Milk, and other kinds of Supping Meats, presently after they are removed from the Fire, get a skin or film on the top of them, but this, that the agitation of the Heat is diminished by the contact of the cold Air, and in a manner quite stopt.

V. Th Surface of Water is smooth, and more difficulty divided than its inward parts. Hence it is also, that the Surface of all Liquors is smooth and even; for tho' the Parts of Water be uniformly moved, as well as the Air, which immediately toucheth them; yet because the parts of the Water are moved after another man∣ner, than those of the Air; and that the Subtil

matter which surrounds the parts of the Air is quite otherwise moved than that which swims amongst the particles of the water; by this means the sur∣face of either of them becomes smooth, much af∣ter the same manner as when two Hard Bodies are rub'd against one another; only with this diffe∣rence, that this smoothness is with much more ease produced in liquid Bodies, because of the easie and ready Mobility of their Parts. And this is the reason also why the surface of the wateer is divided with more difficulty, than its inward parts.

VI. The Hard∣ness of Bo∣dies some∣times pro∣ceeds from Cold. Cold also conduceth much to the Hardning of several Bodies: for we see that the surface of wa∣ter in a River, by cold is congealed, whilst that which is at the bottom, by reason of the stronger motion of heat, suffers not the least alteration; and so also are many other Bodies sometimes hardned by cold, and thereby attain that degree of firmness, which is caused in them, by other Bodies beating upon them: For frozen Fruit, if it be put into cold water, and set in a warmish place, will ap∣pear covered over with a Crust of Ice, and in like manner the Flesh of Beasts or Fish that is frozen, if it be set in a warm place covered with Snow, there will appear a hard Crust of Ice on the sur∣face of it.

VII. But more naturally from Heat. But tho' cold may sometimes contribute to the hardning of Bodies, yet this effect may with greater Right be attributed to Heat, whose property it is to agitate the parts of Bodies, and bring them closer together, by exhaling their superfluous moi∣sture. Thus a Body exposed to the Beams of the Sun, as by this means it becomes better digested and riper; so likewise it attains a greater degree of firmness and hardness. This is manifest in Apples, Pears, Cherries, Plums and such like, whose out∣side by the Heat of the Sun becomes hardned, and covered with a Skin.

VIII. All these ways are reducible to one general way of Hardning of Bodies. But which way soever this Hardness may be produced in Bodies, it seems that they are all re∣ducible to one general Cause, forasmuch as their outward parts endure the impulse of other Bodies rushing against them and dashing upon them, and by hindring their ingress, do resist and beat them off.