tity, that in some places I have seen the very High-wayes, neer such Iron-works, mended with Heaps of such Lumps of Glasse, instead of Stones and Gravel. And I have also Observ’d, that some kind of Fire-stone it Self, having been employ’d in Furnaces wherein it was expos’d to very strong and lasting Fires, has had all its Fixt Parts so Wrought on by the Fire, as to be Perfectly Vitrifi’d, which I have try’d by Forcing from it Pretty large Pieces of Perfect and Transparent Glass. And lest You might think, Eleutherius, that the Question’d Definition of Heat may be Demonstrated, by the Definition which is wont to be given and Acquiesc’d in, of its contrary Quality, Cold, whose property is taught to be tam Homogenea, quam Heterogenea congregare ; Give me leave to represent to You, that neither is this Definition unquestionable; for not to Mention the Exceptions, which a Logician, as such, may Take at it, I Consider that the Union of Heterogeneous Bodies which is Suppos’d to be the Genuine Production of Cold, is not Perform’d by every Degree of Cold. For we see for Instance that in the Urine of
