that violent fire of the green Glass-house; but, if yet it be doubted, let Experiment be further made with that body that is accounted, by Chymists and others, the most ponderous and fix’d in the world; for by heating of a piece of Gold, and proceeding in the same manner, you may find the same effects. This trembling and shaking of the Rays, is more sensibly caus’d by an actual flame, or quick fire, or anything else heated glowing hot; as by a Candle, live Coal, red-hot Iron, or a piece of Silver, and the like: the same also appears very conspicuous, if you look at an Object betwixt which and your eye, the rising smoak of some Chimney is interpos’d; which brings into my mind what I had once the opportunity to observe, which was, the Sun rising to my eye just over a Chimney that sent forth a copious steam of smoak; and taking a short _Telescope_, which I had then by me, I observ’d the body of the Sun, though it was but just peep’d above the Horizon, to have its underside, not onely flatted, and press’d inward, as it usually is when neer the Earth; but to appear more protuberant downwards then if it had suffered no refraction at all; and besides all this, the whole body of the Sun appear’d to tremble or dance, and the edges or limb to be very ragged or indented, undulating or waving, much in the manner of a flag in the Wind. This I have likewise often observ’d in a hot Sunshiny Summer’s day, that looking on an Object over a hot stone, or dry hot earth, I have found the Object to be undulated or shaken, much after the same manner. And if you look upon any remote Object through a _Telescope_ (in a hot Summer’s day especially) you shall find it likewise to appear tremulous. And further, if there chance to blow any wind, or that the air between you and the Object be in a motion or current, whereby the parts of it, both rarify’d and condens’d, are swiftly remov’d towards the right or left, if then you observe the Horizontal ridge of a Hill far distant, through a very good _Telescope_, you shall find it to wave much like the Sea, and those waves will appear to pass the same way with the wind. From which, and many other Experiments, ’tis cleer that the lower Region of the Air, especially that part of it which lieth neerest to the Earth, has, for the most part, its constituent parcels variously agitated, either by heat or winds, by the first of which, some of them are made more rare, and so suffer a less refraction; others are interwoven, either with ascending or descending vapours; the former of which being more light, and so more rarify’d, have likewise a less refraction; the latter being more heavie, and consequently more dense, have a greater.