Note 7 — Chapter II · FORM, STRUCTURE, AND COMPOSITION OF VOLCANIC MOUNTAINS.

Whymper states that there is a prevalent idea that Cotopaxi and a volcano called Sangai act as safety-valves to each other. Sangai reaches an elevation (according to Reiss and Stübel) of 17,464 feet, and sends intermittent jets of steam high into the air, spreading out into vast cumulus clouds, which float away southwards, and ultimately disappear.—Ibid., p. 73.