Cross-sectional diagram of a geyser: “Let us suppose a cavity C, communicating with the pipe PQ, filled with boiling water to the height AB, and that the steam above this line is conﬁned so that it sustains the water to the height P. If we suppose a sudden addition of heat to be applied under the cavity C, a quantity of steam will be produced which, owing to the great pressure, will be evolved in starts causing the noises like discharges of artillery, and the shaking of the ground.”