But Ice will dissolve in any way of heat, for it will dissolve with fire, it will colliquate in water, or warm oyl; nor doth it only submit unto an actual heat, but not endure the potential calidity of many waters. For it will presently dissolve in cold _Aqua fortis_, sp. of Vitriol, Salt, or Tartar, nor will it long continue its fixation in spirits of Wine, as may be observed in Ice injected therein. Again, The concretion of Ice will not endure a dry attrition without liquation; for if it be rubbed long with a cloth, it melteth. But Crystal will calefie unto electricity, that is, a power to attract straws or light bodies, and convert the needle freely placed. Which is a declarement of very different parts, wherein we shall not inlarge, as having discoursed concerning such bodies in the Chap. of Electricks. They are differenced by supernatation or floating upon water; for Crystal will sink in water, as carrying in its own bulk a greater ponderosity then the space in any water it doth occupy; and will therefore only swim in molten Metal and Quicksilver. But Ice will swim in water of what thinness soever; and though it sink in oyl, will float in spirits of Wine or _Aqua vitæ_. And therefore it may swim in water, not only as being water it self, and in its proper place, but perhaps as weighing somewhat less then the water it possesseth. And therefore as it will not sink unto the bottom, so will it neither float above like lighter bodies, but being near in weight, lie superficially or almost horizontally unto it. And therefore also an Ice or congelation of Salt or Sugar, although it descend not unto the bottom, yet will it abate, and decline below the surface in thin water, but very sensibly in spirits of Wine. For Ice although it seemeth as transparent and compact as Crystal, yet is it short in either; for its atoms are not concreted into continuity, which doth diminish its translucency; it is also full of spumes and bubbles, which may abate its gravity. And therefore waters frozen in Pans, and open Glasses, after their dissolution do commonly leave a froth and spume upon them, which are caused by the airy parts diffused in the congealable mixture which uniting themselves and finding no passage at the surface, do elevate the mass, and make the liquor take up a greater place then before: as may be observed in Glasses filled with water, which being frozen, will seem to swell above the brim. So that if in this condensation any one affirmeth there is also some rarefaction, experience may assert it.