The History.

A TABLE SHOWING THE CONTRACTION AND EXPANSION OF MATTER IN RESPECT OF SPACE, IN TANGIBLE BODIES (SUCH AS ARE ENDOWED WITH WEIGHT); WITH A COMPUTATION OF THE PROPORTIONS IN DIFFERENT BODIES.

The manner of

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the experiment

the foregoing

Table.

The weights here used are the same as

with respect to those used by goldsmiths; the pound consisting of 12 ounces, the ounce of 20 pennyweights, and the pennyweight of 20 grains. And I chose pure gold as the standard to which other bodies should be referred; because gold is not only the heaviest, but likewise the most uniform and consistent substance there is; having nothing volatile about it. The experiment was this: I formed an ounce of pure gold into the shape of a die or cube; I then prepared a small hollow prism of silver in which the cube of gold might be placed so as exactly to fit; only that the height of the prism was somewhat greater; the place inside to which the top of the cube reached being however marked with a conspicuous line. This I did for the sake of fluids and powders; that when a fluid was

poured into the prism up to that height, it might have a little margin to keep it from overflowing. At the same time I had another prism made, exactly equal to the other in weight and dimension; that the two prisms being in all respects alike, the proportions of the bodies contained therein might be exactly compared. Next I had cubes made of the same size and dimension in all the matters specified in the Table, that admit of being cut into that shape; but fluids I made trial of at once, by filling the prism with the fluid up to the line that had been marked. And I did the same with powders; first pressing them together as close as possible; for this tends to make them uniform, and excludes accidental differences. Therefore the trial was no other than this; one of the prisms was placed in one scale empty; the other with the body in it in the other; and so the weight of the body contained was taken separately. Now, by how much the weight of a body is less than the weight of gold, by so much is the bulk of that body greater than the bulk of gold. As for example, since the cube of gold weighs one ounce, and the cube of myrrh one pennyweight, it is manifest that the bulk of myrrh in proportion to the bulk of gold is as twenty to one; so that there is twenty times as much matter in gold as in an equal bulk of myrrh; and again there is twenty times as much bulk in myrrh as in an equal weight of gold.

Admonitions.

1. The smallness of the vessel employed, and the shape also (though convenient for receiving these cubes), were not favourable for verifying the exact proportions. For it was not easy to take differences of weight below a quarter of a

grain; and besides, in that square surface a slight and insensible increase of height might carry with it a sensible difference in weight, which is not the case in vessels which rise to a point.

2. No doubt but many of the bodies set down in the Table admit of more and less, as to gravity and bulk, in their own species. For both wines and

woods of the same species vary in weight, some being certainly heavier than others; and so do certain other of the substances enumerated. Therefore with respect to nice calculation there is some uncertainty. And moreover those individuals with which my experiment deals may not represent exactly the nature of their species, nor perhaps agree to a nicety with the experiments of others.

3. In the above Table I have included such bodies as could conveniently be made to fill up the space or measure, the body remaining entire and uniform; and such likewise as have weight; from the proportion of which I formed a judgment of the amount of matter collected. There are therefore three kinds of bodies which could not be included; first, those which will not go into the shape of a cube, as leaves, flowers, pellicles, and membranes; secondly, those which are unequally hollow and porous, as sponge, cork, and wool; and thirdly, pneumatic bodies, as air and flame, because they are not endowed with weight.

4. It should be observed whether the close contraction of a body may not, by reason of the union of force, give it a greater degree of weight than in proportion to the quantity of matter. Whether this be so or not should be inquired from the particular

history of Gravity. If it be so, the calculation no doubt fails; and the more rarefied a body is, the more matter will it contain within the same bulk than would appear from a calculation founded upon the weight as compared with the measurement. This Table I constructed many years ago, and (as I recollect) took considerable pains about it. But a much more accurate Table may no doubt be made ; consisting of a greater number of bodies, measured on a larger scale; a thing that contributes greatly to exactness in the matter of proportions. And seeing that this is fundamental to the subject, such a Table should by all means be prepared.

Observations.

1. Here we may observe with satisfaction how finite and comprehensible the nature of things is in tangible bodies. For the Table brings nature as it were within the grasp. Let no one wander off therefore, or indulge in fancies and dreams. In this Table there is no substance found that exceeds any other substance in quantity of matter beyond the proportion of 32 to 1; which is the proportion in which gold exceeds fir wood. Of things in the interior of the earth however I say nothing, seeing that they are not subject either to sense or experiment. These, it may be, being both far removed and completely separated from the heat of the heavenly bodies, are more dense than any known bodies.

2. The opinion that all sublunary bodies are composed of the four elements is ill borne out. For the cube of gold in the prism weighed 20 pennyweights; the common earth only a little more than 2; water 1