salt employ'd to bring the sand to fusion, I found that the knowingst Workmen imputed these Mis-adventures to the Ashes, of [Errata: Ashes off] some certain kind of Wood, as having observ'd the ignobler kind of Glass I lately mention'd to be frequently produc'd when they had employ'd such sorts of Ashes which therefore they scruple to make use of, if they took notice of them beforehand. I remember also, that an Industrious Man of my acquaintance having bought a vast quantity of Tobacco stalks to make a fixt Salt with, I had the Curiosity to go see whether that Exotick Plant, which so much abounds in volatile salt, would afford a peculiar kind of _Alcali_; and I was pleas'd to find that in the _Lixivium_ of it, it was not necessary, as is usual, to evaporate all the Liquor, that there might be obtain'd a Saline Calx, consisting like lime quench'd in the Air of a heap of little Corpuscles of unregarded shapes; but the fixt salt shot into figur'd Crystal, almost as Nitre or _Sal-armoniack_ and other uncalcin'd salts are wont to do; And I further remember that I have observ'd in the fixt Salt of Urine, brought by depuration to be very white, a tast not so unlike to that of common salt, and very differing from the wonted caustick Lixiviate tast of other salts made by Incineration. But because the Instances I have alledg'd of the Difference of _Alcalizate_ salt are but few, and therefore I am still inclin'd to think, that most Chymists and many Physitians do, inconsideratly enough and without Warrant from Experience, ascribe the Vertues of the Concretes expos'd to Calcination, to the salts obtain'd by it; I shall rather, to shew the Disparity of salts, mention in the first Place the apparent Difference betwixt the Vegetable fixt salts and the Animal Volatile ones: As (for Example) betwixt salt of Tartar, and salt of Harts-horn; whereof the former is so fixt that 'twill indure the brunt of a violent Fire, and stand in fusion like a Metal; whereas the other (besides that it has a differing tast and a very differing smell) is so far from being fixt, that it will fly away in a gentle heat as easily as Spirit of Wine it self. And to this I shall add, in the next place, That even among the Volatile salts themselves, there is a considerable Difference, as appears by the distinct Properties of (for Instance) salt of Amber, salt of Urine, salt of Mans Skull, (so much extoll'd against the falling Sicknesse) and divers others which cannot escape an ordinary Observer. And this Diversity of Volatile salts I have observ'd to be somtimes Discernable even to the Eye, in their Figures. For the salt of Harts-horn I have observ'd to adhere to the Receiver in the forme almost of a _Parallelipipedon_; and of the Volatile salt of humane blood (long digested before distillation, with spirit of Wine) I can shew you store of graines of that Figure which _Geometricians_ call a _Rhombus_; though I dare not undertake that