Note 22 — The Mineral Constitution and Microscopic Characters of some of the Lavas of Etna.

The figures in this plate are magnified 35 diameters. Fig. 1. Lava of b.c. 396. The upper half of the drawing is occupied by a crystal of plagioclastic felspar showing twin lamellation and faint zonal markings, and with numerous irregular dark-brown inclosures of glass, probably containing magnetite dust and matter similar to that of the groundmass of the rock which consists of felspar microliths, granules of olivine, and augite crystals, grains of magnetite, and apparently a little interstitial glass. A crystal of augite is shown near the bottom of the drawing.

Fig. 2. Lava of a.d. 1689. On the right hand side part of a plagioclase crystal with inclosures similar to that in the preceding figure. In the centre a small crystal of plagioclase. Groundmass similar to that of Fig. 1, but showing a somewhat definite arrangement of the small felspar crystals, indicative of fluxion.