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 Refraction equally with that Part we call the Root.

That the Spar formed in Fiures of Rocks, is thus wahed out of the Limetone itelf is certain:

Becaue none but Limetone Rocks have Spar in their Fiures; Rocks of Crytaline Matter, or formed of vitrifiable Stone, have Crytal; never Spar in their Cracks.

Linnæus wonders at the Nature of that Force which plit the Rocks into thee Cracks: But probably the Caue is very familiar; they were formed moit, and cracked in drying.

Spar grows continually; for whereoever there is a Crack in a Limetone Rock, new, or old; Spar always fills it; and over-runs the Surface.

Letters cut hollow in a living Rock of Limetone, fill up, in a Coure of Years, with Spar; and what were made in Creux are found in Relief. This has been een in Gothland by the eminent Swede; and in the Grotto of Antiparos by Tournefort. The very Time may be determined by the Dates, which are often a Part of the Incription; but it is always long. The Spar tands higher as the Time is more ditant: and has been feen in ome Places a Quarter of an Inch above the Level of the Surface.

If there could want a Proof of the continual Growth of Spar, the Stalactites would hew it; and the Incrutations, in what are called our petrifying