Abbildungen der Seite

... It is no small advantage of this table to demonstrate, that all the variety found in the nu" merous tangible bodies known to us, (which are compact, and neither spongy, hollow, nor in great part filled with air) exceeds not the proportion of twenty-two to one". So finite a thing is nature, at least that part thereof whose use principally regards ourselvest. We also thought it worth trying to discover the proportions of untangible, or pneumatic bodies, with respect to such as are tangible, for which purpose we took an ounce vial, chušing it small that the following evaporation might be performed with the less heat. This vial we filled almost to the neck, with such spirit of wine as we observed by the table mentioned above, to be specifically lighter, or to contain less matter under the same dimension, than all other tangible bodies that are close and compact. Then we exactly marked down the weight of the spirit, and the vial together. After this, we took a bladder, containing about a quart, and squeezed all the air out, as near as possible, till the sides of the bladder collapsed, and became contiguous, having first gently oiled it, to render it the closer or tighter, by filling up the pores, if there were any. This bladderwe strongly tied with a wax thread about the neck of the vial, putting the mouth of the vial into the neck of the bladder, then setting the vial upon a chafing-dish of warm embers, the vapour of the spirit, dilated by the heat, and thus rendered pneumatical, gradually distended or swelled out the bladder every way, like a sail. Then we immediately removed the glass from the fire, and placed it upon a carpet, to prevent its breaking by the cold, and now we directly made a hole in the upper part of the bladder, lest the vapour, as the heat diminished, should fall back, or icondense into liquor, and disturb the calculation: Then taking away the bladder, we weighed the remaining spirit of wine, and thence computed how much was wasted in vapour; and, by com: parison, calculating how much space the body possessed in the form of spirit of wine in the vial; and again, how much it possessed when rendered pneumatical in the bladder, it plainly appeared, that the body, so converted and changed, acquired a degree of extension a hundred times greater than it had before. . . o og

* Suppose the difference in specific gravity between gold and spirit of wine.

t Viz. The tangible part. ...? le - -- - -

: ... ... onto, oi, so *

-: ****

In like manner, let the nature sought be heat. or cold, so weak in degree as to be imperceptible.

[ocr errors]

These are brought to the sense by means of a weather-glass, such as we have above described", wherein heat expands, and cold contracts the air. Neither is this expansion and contraction of the air perceptible by sight; but the air, when expanded, depresses water, and when contracted, raises it up; and thus alone it is that the thing becomes visible and sensible, and not otherwise. In like manner, let the subject of enquiry be the mixture of bodies, to determine what they contain that is aqueous, oleaginous, spirituous, saline, earthy, &c. or, in particular, how much butter is contained in milk, how much curd, how much whey, &c. All these things are reduced and brought down to the senses by artificial and skilful preparations, exhibited in the form of tangible bodiest. But the nature of the spirit in them, though not immediately perceived, is discovered by the various motions and endeavours of tangible bodies, in the act and process of their separation, as also by the acrimony, corrosiveness, different colours, smells and tastes of the same bodies after separation. 2 And, with regard hereto, men have bestowed

great pains upon distillations, and artificial se* ~ * - -

[ocr errors]
[ocr errors]

* Aph, 1s. " ' * As in all those called Chemical Analyses, or Resolutions. parations, but not with much better success-than in the other experiments hitherto practised, as having proceeded altogether by feeling out their way in blind roads, or with more labour than understanding; and, what is worse, without imitating, copying, or rivalling nature, but by their violent heats, and overpowerful operations, destroying all the subtilty of structure, in which the secret virtues and relations of things are principally seated”.


Nor have men, as we elsewhere observed h, hitherto taken notice with regard to this kind of separations, that numerous qualities, in the torturing of bodies, as well by fire as otherwise, proceed from the fire itself, and the matters employed in the separation, which qualities were not before in the composition; whence strange fallacies have arisen. Thus all the vapour which water emits by fire, is not the vapour, or air, before existing in the body of the water, but in great measure produced by the dilatation of the water, through the interposition of the heat of the fire.

* Hence there are few genuine separations to be found in the common chemistry, even as practised by the best hands. See the Sylva Sylvarum, under the article Gold, &c. * See above Part II. Aph. 7. and the Sylva Sylvarum. *

* * * * * * * .


-** ***

So likewise, in general, all exquisite trials and examinations of bodies, whether natural or artificial, made to distinguish the genuine from the adulterate, and the better from the worse, should be referred to this head, as these also make what is insensible to appear sensible, and therefore are, with great care, to be collected from all quarters”. - 'i

As to the fifth way of concealment from the senses, it is manifest that the action of sense is performed in motion, and motion in time, whence, if the motion of any body be either so slow, or so swift, as not to be proportioned to the moments wherein the act of sensation is performed, the object will not be perceived, as we find in the motion of the hand of a clock, and the motion of a bullet discharged from a gun.

But the motion which is not perceived through its slowness, is easily and commonly reduced to sense, by the result or amount of the motion ; but that which is imperceptible through its velocity, is not hitherto well measured, yet the enquiry of nature demands that this should be done in some casest.

* See Mr. Boyle's Medicina Hydrostatica; and the De Augmentis Scientiurum. # Thus the motion of sounds, and even of light, which seems the swiftest motion of all, is now reduced to calculation. See the Author's History of Sounds, in the Sylva SylWOL. II. h

« ZurückWeiter »