Nor is _Marble_ the only seemingly close stone, which by other kinds of Experiments may be found porous; for I have by this kind of Experiment on divers other stones found much the same effect, and in some, indeed much more notable. Other stones I have found so porous, that with the _Microscope_ I could perceive several small winding holes, much like Worm-holes, as I have noted in some kind of _Purbeck-stone_, by looking on the surface of a piece newly flaw’d off, for if otherwise, the surface has been long expos’d to the Air, or has been scraped with any tool, those small caverns are fill’d with dust, and disappear. And to confirm this _Conjecture_, yet further, I shall here insert an excellent account, given into the _Royal Society_ by that Eminently Learned Physician, Doctor _Goddard_, of an Experiment, not less instructive then curious and accurate, made by himself on a very hard and seemingly close stone call’d _Oculus Mundi_, as I find it preserv’d in the Records of that Honourable Society. A small stone of the kind, call’d by some Authours, _Oculus Mundi_, being dry and cloudy, weigh’d 5²⁰⁹⁄₂₅₆ _Grains_. The same put under water for a night, and somewhat more, became transparent, and the superficies being wiped dry, weighed 6³⁄₂₅₆ _Grains_. The difference between these two weights, 0⁵⁰⁄₂₅₆ of a _Grain_. The same Stone kept out of water one Day and becoming cloudy again weighed, 5²²⁵⁄₂₅₆ _Graines_. Which was more then the first weight, 0¹⁶⁄₂₅₆ of a _Grain_. The same being kept two Days longer weighed, 5²⁰²⁄₂₅₆ _Graines_. Which was less then at first, 0⁷⁄₂₅₆ a _Grain_. Being kept dry something longer it did not grow sensibly lighter. Being put under water for a night and becoming again transparent and wiped dry, the weight was, _6³⁄₂₅₆ Grains_, the same with the first after putting in water, and more then the last weight after keeping of it dry, 0⁵⁷⁄₂₅₆ of a _Grain_. Another Stone of the same kind being variegated with milky _white_ and _gray_ like some sorts of _Agates_, while it lay under water, was alwaies invironed with little Bubbles, such as appear in water a little before boyling, next the sides of the Vessel. There were also some the like Bubbles on the Surface of the water just over it, as if either some exhalations came out of it, or that it did excite some fermentation in the parts of the water contiguous to it. There was little sensible difference in the transparency of this Stone, before the putting under water, and after: To be sure the milky-_white_ parts continued as before, but more difference in weight then in the former. For whereas before the putting into the water the weight was 18⁹⁷⁄₁₂₈ _Graines_. After it had lyen in about four and twenty hours the weight was 20²⁷⁄₁₂₈ _Graines_, so the difference was, 1⁵⁸⁄₁₂₈ _Graines_.