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We find hollow Cryſtals, and we have hollow Pyramids of Spar; but 'tis a raſh Thought, tho' of a great Man, to imagine that a Cryſtal of Salt was firſt formed in theſe Caſes; and when the ſtony Coat was finiſhed over, it melted away again: This is Imagination: But there is not a hollow Stalactite that may not ſhew the Senſes, and convince the Reaſon, that this Shell of Spar, or Cryſtal, may be formed without a ſolid Nucleus.
There are no entire Rocks of Spar; and they who thought they had ſeen ſuch of Cryſtal, perhaps miſtook pure Ice for them. Both Spar and Cryſtal rife in general from foul Stones; and they who thought Ice grew to them in Time, were ſcarce more pardonable than ſuch as took Ice for them. Scheukzer has ſeen the Difficulty of accounting for their Forms, and joined the Lamentation of Philoſophers upon that Subject; for the Salt Syſtem was not then in being: But the old Pliny has not only lamented this Difficulty, but aſſigned its Cauſe; and this a Cauſe to overthrow that Syſtem utterly: It is, that tho' the Figures be all regular, they are not all alike; or all reſolvable into the ſame Laws.
'Tis an invidious Office, and unpleaſing, to dwell upon the Errors of thoſe who wrote before; but theſe are ſo received, and ſo eſtabliſhed, that there is no other Way to Truth.
Wallerius ſays, that Spar is compoſed of rhombic and pyramidal Particles: And there-
