VI. Of Small Glass Canes.
That I might be satisfied, whether it were not possible to make an Artificial pore as small as any Natural I had yet found, I made several attemps with small glass pipes, melted in the flame of a Lamp, and then very suddenly drawn out into a great length. And, by that means, without much difficulty, I was able to draw some almost as small as a Cobweb, which yet, with the Schem. 4. Microscope, I could plainly perceive to be perforated, both by looking on the ends of it, and by looking on it against the light which was much the easier way to determine whether it were solid or perforated; for, taking a small pipe of glass, and closing one end of it, then filling it half full of water, and holding it against the light, I could, by this means, very easily find what was the differing aspect of a solid and a perforated piece of glass; and so easily distingish, without seeing either end, whether any Cylinder of glass I look'd on, were a solid stick, or a hollow cane. And by this means, I could also presently judge of any small filament of glass, whether it were hollow or not, which would have been exceeding tedious to examine by looking on the end. And many such like ways I was fain to make use of, in the examining of divers other particulars related in this Book, which would have been no easie task to have determined meerly by the more common way of looking on, or viewing the Object. For, if we consider first, the very faint light wherewith the object is enlightened, whence many particles appear opacous, which when more enlightned, appear very transparent, so that I was fain to determine its transparency by one glass, and its texture by another. Next, the unmanageableness of most Objects, by reason of their smalness, 3. The difficulty of finding the desired point, and of placing it so, as to reflect the light conveniently for the Inquiry. Lastly, ones being able to view it but with one eye at once, they will appear no small obstructions, nor are they easily remov'd without many contrivances. But to proceed, I could not find that water, or some deeply ting'd liquors would in small ones rise so high as one would expect; and the highest I have found it yet rise in any of the pipes I have try'd, was to 21 inches above the level of the water in the vessel: for though I found that in the small pipes it would nimbly enter at first, and run about 6 or 7 inches upwards; yet I found it then to move upwards so slow, that I have not yet had the patience to observe it above that height of 21 inches (and that was in a pretty large Pipe, in comparison of those I formerly mentioned; for I could observe the progress of a very deep ting'd liquor in it with my naked eye, without much trouble; whereas many of the other pipes were so very small, that unless in a convenient posture to the light, I could not perceive them:) But 'tis very probable, that a greater patience and assiduity may discover the liquors to rise, at least to remain suspended, at heights that I should be loath now even to ghess at, if at least there be any proportion kept between the height of the ascending liquor, and the bigness of the holes of the pipes.
An Attempt for the Explication of this Experiment.
My Conjecture, That the unequal height of the surfaces of the water, proceeded from the greater pressure made upon the water by the Air Schem. 4. Fig. 1. without the Pipes ABC, then by that within them I shall endeavour to confirm from the truth of the two following Propositions:
The first of which is, That an unequal pressure of the incumbent Air, will cause an unequal height in the water's Surfaces.
And the second is, That in this experiment there is such an unequal pressure.
That the first is true, the following Experiment will evince. For if you take any Vessel so contrived, as that you can at pleasure either increase or diminish the pressure of the Air upon this or that part of the Superficies of the water, the equality of the height of those parts will presently be lost; and that part of the Superficies that sustains the greater pressure, will be inferior to that which undergoes the less. A fit Vessel for this purpose, will be an inverted Glass Syphon, such an one as is described in the Sixth Figure. For if into it you put Water enough to fill it as high as AB, and gently blow in at D, you shall depress the Superficies B, and thereby raise the opposite Superficies A to a considerable height, and by gently sucking you may produce clean contrary effects.
Next, That there is such an unequal pressure, I shall prove from this, That there is a much greater incongruity of Air to Glass, and some other Bodies, then there is of Water to the same.
By Congruity, I mean a property of a fluid Body, whereby any part of it is readily united with any other part, either of itself, or of any other Similar, fluid, or solid body: And by Incongruity a property of a fluid, by which it is hindred from uniting with any dissimilar, fluid, or solid Body.
This last property, any one that hath been observingly conversant about fluid Bodies, cannot be ignorant of. For (not now to mention several Chymical Spirits and Oyls, which will very hardly, if at all, be brought to mix with one another; insomuch that there may be found some 8 or 9, or more, several distinct Liquors, which swimming one upon another, will not presently mix) we need seek no further for Examples of this kind in fluids, then to observe the drops of rain falling through the air and the bubbles of air which are by any means conveyed under the surface of the water; or a drop of common Sallet Oyl swimming upon water. In all which, and many more examples of this kind that might be enumerated, the incongruity of two fluids is easily discernable. And as for the Congruity or Incongruity of Liquids, with several kinds of firm Bodies, they have long since been taken notice of, and called by the Names of Driness and Moisture (though these two names are not comprehensive enough, being commonly used to signifie only the adhering or not adhering of water to some other solid Bodies) of this kind we may observe that water will more readily wet some woods then others; and that water, let fall upon a Feather, the whiter side of a Colwort, and some other leaves, or upon almost any dusty, unctuous, or resinous superficies, will not at all adhere to them, but easily tumble off from them, like a solid Bowl; whereas, if dropt upon Linnen, Paper, Clay, green Wood, &c. it will not be taken off, without leaving some part of it behind adhering to them. So Quick-silver, which will very hardly be brought to stick to any vegetable body, will readily adhere to, and mingle with, several clean metalline bodies.
And that we may the better finde what the cause of Congruity and Incongruity in bodies is, it will be requisite to consider, First, what is the cause of fluidness; And this, I conceive, to be nothing else but a certain pulse or shake of heat; for Heat being nothing else but a very brisk and vehement agitation of the parts of a body (as I have elswhere made probable) the parts of a body are thereby made so loose from one another, that they easily move any way, and become fluid. That I may explain this a little by a gross Similitude, let us suppose a dish of sand set upon some body that is very much agitated, and shaken with some quick and strong vibrating motion, as on a Milstone turn'd round upon the under stone very violently whilst it is empty; or on a very stiff Drum-head, which is vehemently or very nimbly beaten with the Drumsticks. By this means, the sand in the dish, which before lay like a dull and unactive body, becomes a perfect fluid; and ye can no sooner make a hole in it with your finger, but it is immediately filled up again, and the upper surface of it levell'd. Nor can
