I took a pretty large piece of this stone, and covering it all over with cement, save only at two opposite parts, I found my self able, by blowing in at one end that was left open, to blow my spittle, with which I had wet the other end, into abundance of bubbles, which argued these pores to be open and pervious through the whole stone, which affords us a very pretty instance of the porousness of some seemingly close bodies, of which kind I shall anon have occasion to subjoyn many more, tending to prove the same thing. I must not here omit to take notice, that in this body there is not a _vegetative_ faculty that should so contrive this structure for any peculiar use of _Vegetation_ or growth, whereas in the other instances of vegetable porous bodies, there is an _anima_ or _forma informans_, that does contrive all the Structures and _Mechanisms_ of the constituting body, to make them subservient and usefull to the great Work or Function they are to perform. And so I ghess the pores in Wood, and other vegetables, in bones, and other Animal substances, to be as so many channels, provided by the Great and Alwise Creator, for the conveyance of appropriated juyces to particular parts. And therefore, that this may tend, or be pervious all towards one part, and may have impediments, as valves or the like, to any other; but in this body we have very little reason so suspect there should be any such design, for it is equally pervious every way, not onely forward, but backwards, and side-ways, and seems indeed much rather to be _Homogeneous_ or similar to those pores, which we may with great probability believe to be the channels of _pellucid_ bodies, not directed, or more open any one way, then any other, being equally pervious every way. And, according as these pores are more or greater in respect of the _interstitial_ bodies, the more transparent are the so constituted concretes; and the smaller those pores are, the weaker is the _Impulse_ of light communicated through them, though the more quick be the progress. Upon this Occasion, I hope it will not be altogether unseasonable, if I propound my conjectures and _Hypothesis_ about the _medium_ and conveyance of light. I suppose then, that the greatest part of the _Interstitia_ of the world, that lies between the bodies of the Sun and Starrs, and the Planets, and the Earth, to be an exceeding fluid body, very apt and ready to be mov’d, and to communicate the motion of any one part to any other part, though never so far distant: Nor do I much concern my self, to determine what the Figure of the particles of this exceedingly subtile fluid _medium_ must be, nor whether it have any interstitiated pores or vacuities, it being sufficient to solve all the _Phænomena_ to suppose it an exceedingly fluid, or the most fluid body in the world, and as yet impossible to determine the other difficulties. That being so exceeding fluid a body, it easily gives passage to all other bodies to move to and fro in it.