It is a diametrically opposite cause to this that produces crystal,[2936] a substance which assumes a concrete form from excessive congelation.[2937] At all events, crystal is only to be found in places where the winter snow freezes with the greatest intensity; and it is from the certainty that it is a kind of ice, that it has received the name[2938] which it bears in Greek. The East, too, sends us crystal, there being none preferred to the produce of India. It is to be found, also, in Asia, that of the vicinity of Alabanda,[2939] Orthosia,[2940] and the neighbouring mountains, being held in a very low degree of esteem. In Cyprus, also, there is crystal, but that found upon the Alpine heights in Europe is, in general, more highly valued. According to Juba, there is crystal in a certain island of the Red Sea, opposite the coast of Arabia, called “Necron;”[2941] as, also, in another neighbouring island[2942] which produces the precious stone known as the “topazus;” where a block of crystal was extracted, he says, by Pythagoras, the præfect of King Ptolemæus, no less than a cubit in length. Cornelius Bocchus informs us that in Lusitania, there have been blocks of crystal found, of extraordinary weight, in sinking shafts in the Ammiensian[2943] mountains there, to a water-level for the supply of wells. It is a marvellous fact, stated by Xenocrates of Ephesus, that in Asia and in the Isle of Cyprus, crystal is turned up by the plough; it having been the general belief that it is never to be found in terreous soils, and only in rocky localities. That is much more probable which the same Xenocrates tells us, when he says that the mountain streams often bring down with them fragments of crystal. Sudines says, that crystal is only to be found in localities that face the south, a thing that is known to be really the fact: indeed, it is never found in humid spots, however cold the climate may be, even though the rivers there freeze to the very bottom. Rain-water and pure snow are absolutely necessary for its formation,[2944] and hence it is, that it is unable to endure heat, being solely employed for holding liquids that are taken cold. From the circumstance of its being hexagonal[2945] and hexahedral, it is not easy to penetrate this substance; and the more so, as the pyramidal terminations do not always have the same appearance. The polish on its faces is so exquisite, that no art can possibly equal it. CHAP. 10.—LUXURY DISPLAYED IN THE USE OF CRYSTAL. REMEDIES DERIVED FROM CRYSTAL.