THE
International Scientific Series
VOL. XXXV.
Frontispiece.
Sections of Igneous Rocks, illustrating the passage from the glassy to the crystalline structure.
1. Vitreous Rock. 2. Semi-Vitreous Rock. 3. Vitreous Rock with Sphærulites. 4. Rock with Crypto-crystalline Base. 5. Rock with Micro-crystalline Base. 6. Rock of Granite Structure built up entirely of Crystals.
[See pp. [63-68].
VOLCANOES
WHAT THEY ARE and WHAT THEY TEACH
BY