The Figure and bigness of these for the most part was the same with that of the Figure Z; that is, all the surface of them was very smooth and polisht, and for the most part round, but very rugged or knobbed about D, and all the length of the stem was here and there pitted or flatted. About D, which is at the upper part of the drop under that side of the stem which is concave, there usually was made some one or more little Hillocks or Prominences. The drop it self, before it be broken, appears very transparent, and towards the middle of it, to be very full of small Bubbles, of some kind of aerial substance, which by the refraction of the outward surface appear much bigger then really they are; and this may be in good part removed, by putting the drop under the surface of clear Water, for by that means most part of the refraction of the convex Surface of the drop is destroyed, and the bubbles will appear much smaller. And this, by the by, minds me of the appearing magnitude of the _aperture_ of the _iris_, or _pupil_ of the eye, which though it appear, and be therefore judged very large, is yet not above a quarter of the bigness it appears of, by the _lenticular_ refraction of the _Cornea_. The cause of all which _Phænomena_ I imagine to be no other then this, That the Parts of the Glass being by the excessive heat of the fire kept off and separated one from another, and thereby put into a kind of sluggish fluid Consistence, are suffered to drop off with that heat or agitation remaining in them, into cold Water; by which means the outsides of the drop are presently cool’d and _crusted_, and are thereby made of a loose texture, because the parts of it have not time to settle themselves leisurely together, and so to lie very close together: And the innermost parts of the drop, retaining still much of their former heat and agitations, remain of a loose texture also, and, according as the cold strikes inwards from the bottom and sides, are quenched, as it were, and made rigid in that very posture wherein the cold finds them. For the parts of the _crust_ being already hardened, will not suffer the parts to shrink any more from the outward Surface inward; and though it shrink a little by reason of the small parcels of some Aerial substances dispersed through the matter of the Glass, yet that is not neer so much as it appears (as I just now hinted;) nor if it were, would it be sufficient for to consolidate and condense the body of Glass into a _tuff_ and close _texture_, after it had been so excessively rarified by the heat of the glass-Furnace. But that there may be such an expansion of the aerial substance contained in those little _blebbs_ or bubbles in the body of the drop, this following Experiment will make more evident. * * * * *