Bourbon, where the stream, flowing over a precipice, has let t heavy pendent masses resembling the drippings of a guttering candle. Another illustration of the forms produced by very viscid lavas is afforded by the so-called "mamelons" of the island of Bourbon. The flow of rapid

currents is generally accompanied with the disengagement of vast quantities of steam, and this, doubtless, has much to do with the formation of the cindery projections which characterize the cooled surfaces of such streams. Little parasitic volcanoes are often formed on the top of the