and Volcanic. Substances. 215 
of black augit, of Leucite, voleanic hornblende, nepheline, 
Meionite, sommite, Idocrase. Doubts have been entertain- 
ed whether these were pre-existent crystals, or the effect 
and product of igneous fusion, or the effect and product of 
eng Soi filtration into the cells, vesicles and cavities of 
e Lava containing them. See Borkowsky on Sodalite. 
Breislak found a chrystal of Augit inside a chrystal of Leu- 
cite. Inst. § 682. 
Beside these chrystals, the following have been found ac- 
companying Lava ; Garnet, Hyaci inth, Zircon, Sap- 
pene. Spinelle, Peridot, Epidot, titaniferous sidero-calcite, 
remolite, Gyps, Hauyene, Zeolyte, Sodalite, Tafelspar, 
Topaz, Humite (Bournon.) In pe we need not won- 
der at finding the minerals which accompany primi- 
tive rocks, accompanying Lava also ; sometimes chang- 
ed, sometimes unchanged. I Spalan. 78. In the vesi- 
cles or cells of Lava, the minerals commonly found, are 
Leucite (in Italy) Peridot, Zeolyte of various kinds, Preh- 
nite carbonat of lime as at Et tna, at Lipari, 3 Spalan. 228, 
in Iceland. 7. Ed. Trans. 90. Quartz, Agate, chalcedony, 
green earth. Forming amygdaloids, toadstones and geo- 
es; the crystals in the cells are probably infiltrated. 
Various specimens of these, are in every cabinet of tolera- 
ble extent. The Lavas containing crystals are or less 
perfect, of Felspar, are porphyritic Lavas. s contain- 
ing Zeolite, Prehnite, Agate Chalcedony, Sauteed nouv. 
Dict. @hist. natur. Tome 17, p. 390. vas cut through 
all metallic veins, and rarely envelo e any metalline sub- 
stance. Galena is saidto have been found in whin (Kidd 
102.) but such a case is accidental and rare, though very 
possible. Vegetable and animal remains have been found 
adhering to Lava and enclosed init. Breisl. § 700. 1 Humb. 
Pers. Narr. 241, see the question discussed in 3 Breisl. p. 
251. [have a shell adhering to the slag of an iron furnace. 
Lavas are sometimes very extensive. Dolomique notices 
one of ten Jeagues. A stream from the north side of Etna, 
according to upero, extended forty miles. Lord Win- 
cre mentions another in 1669, ace, miles long by 
seven broad. Pennant states the current from Hecla 
in ne at ninety-four miles one way and fifteen another, 
and from eighty to one hundred feet thick. The 
currents in dis Isle of Bourbon produced thirty million tois- 
