ABSTRACT
The sinking of crystals in fluid lava – Specific gravity of the constituent parts of trachyte and of basalt, and their consequent separation – Obsidian – Apparent non-separation of the elements of plutonic rocks – Origin of trap-dikes in the plutonic series – Distribution of volcanic islands; their prevalence in the great oceans – They are generally arranged in lines – The central volcanos of Von Buch doubtful – Volcanic islands bordering continents – Antiquity of volcanic islands, and their elevation in mass -Eruptions on parallel lines of fissure within the same geological period.
