A descriptive account of volcanoes and their phenomena has been presented in this book. A volcano generally presents itself to the imagination as a mountain sending forth from its summit great clouds of smoke with vast sheets of flame, and it is not unfrequently so described. The truth is, however, that a real volcano seldom emits either true smoke or true flame. What is mistaken for smoke consists merely of vast volumes of fine dust, mingled with much steam and other vapours—chiefly sulphurous. What appears like flames is simply the glare from the glowing materials which are thrown up towards the top of the mountain—this glare being reflected from the clouds of dust and steam.