I received your questions in your last: the first was, Whether there be more body compact together in a heavy then in a light thing? I answer, That purity, rarity, little quantity, exteriour shape, as also motion cause lightnesse; and grossness of bulk, density, much quantity, exterior figure and motion cause heaviness, as it may be confirmed by many examples: but lightness and heaviness are onely conceptions of man, as also ascent and descent; and it may be questioned, whether there be such things really in nature; for change of motions of one and the same body will make lightness, and heaviness, as also rarity and density: besides, the several figures and compositions of bodies will cause them to ascend or descend, for Snow is a light body and yet descends from the clouds, and Water is a heavie body, and yet ascends in springs out of the Earth; Dust is a dense body and yet is apt to ascend, Rain or Dew is a rare body and yet is apt to descend; Also a Bird ascends by his shape, and a small worm although of less body and lighter will fall down; and there can be no other proof of light and heavy bodies but by their ascent and descent; But as really there is no such thing as heavie or light in nature more then words, and comparisons of different corporeal motions, so there is no such thing, as high or low, place or time, but onely words to make comparisons and to distinguish different corporeal motions. The second question was; When a Bason with water is wasted into smoak, which fills up a whole Room, Whether the air in the room doth, as the sensitive motions of the eye, pattern out the figure of the smoak; or whether all the room is really fill'd with the vapour or smoak? I answer, If it be onely the pattern or figure of smoak or vapour, the extension and dilation is not so much as man imagines; but why may not the air, which in my opinion hath self-motion, pattern out the figure of smoak as well as the eye; for that the eye surely doth it, may be proved; because smoak, if it enter the eye, makes it not onely smart and water much, but blinds it quite for the present; wherefore smoak doth not enter the eye, when the eye seeth it, but the eye patterns out the figure of smoak, and this is perception; In the same manner may the air pattern out the figure of smoak. The third question was, Whether all that they name qualities of bodies, as thickness, thinness, hardness, softness, gravity, levity, transparentness and the like, be substances? I answer, That all those, they call qualities, are nothing else but change of motion and figure of the same body, and several changes of motions are not several bodies, but several actions of one body; for change of motion doth not create new matter or multiply its quantity: for though corporeal motions may divide and compose, contract and dilate, yet they cannot create new matter, or make matter any otherwise then it is by nature, neither can they add or substract any thing from its nature. And therefore my opinion is, not that they are things subsisting by themselves without matter, but that there can no abstraction be made of motion and figure from matter, and that matter and motion being but one thing and inseparable, make but one substance. Wherefore density and rarity, gravity and levity, &c. being nothing else but change of motions, cannot be without matter, but a dense or rare, heavie or light matter is but one substance or body; And thus having obeyed your commands, I rest,
Madam,
Your faithful Friend,
and Servant.
[XLIV.]
MADAM,
I am very ready to give you my opinion of those two questions you sent me, whereof the first was, Whether that, which is rare and subtil, be not withal pure? To which I answer, That all rare bodies are not subtil, nor pure, and that all which is dense is not gross and dull: As for example, Puddle-water, or also clear water, is rarer then Quicksilver, and yet not so subtil and pure as Quicksilver; the like of Gold; for Quicksilver and Gold may be rarified to a transparentness, and yet be so dense, as not to be easily dissolved; and Quicksilver is very subtil and searching, so as to be able to force other bodies to divide as well as it can divide and compose its own parts. Wherefore my opinion is, that the purest and subtilest degree of matter in nature, is that degree of matter which can dilate and contract, compose and divide into any figure by corporeal self-motion. Your second question was, Why a man's hand cannot break a little hard body, as a little nail, whereas yet it is bigger then the nail? I answer, It is not because the hand is softer then the nail, for one hard body will not break suddenly another hard body, and a man may easily break an iron nail with his hand, as I have bin informed; but it is some kind of motion which can easier do it, then another: for I have seen a strong cord wound about both a man's hands, who pulled his hands as hard and strongly asunder as he could, and yet was not able to break it; when as a Youth taking the same cord, and winding it about his hands as the former did, immediately broke it; the cause was, that he did it with another kind of motion or pulling, then the other did, which though he used as much force and strength, as he was able, yet could not break it, when the boy did break it with the greatest ease, and turning onely his hands a little, which shews, that many things may be done by a slight of motion, which otherwise a great strength and force cannot do. This is my answer and opinion concerning your proposed questions; if you have any more, I shall be ready to obey you, as,
Madam,
Your faithful Friend