The Imbabura volcano, celebrated for its destructive eruptions of mud and water, stands midway between the two ranges at the northern end of the plateau, and belongs to the transverse ridge of knot (_nudo_) which unites them. It is the most northern of the higher peaks of Ecuador, with the exception of Cotocachi, and possibly of Chiles on the Colombian frontier, and reaches the elevation of 15,033 ft. Ibarra on the northern flanks of the volcano has suffered severely from its eruptions. The name is derived from _imba_, fish, and _bura_, mother, and is said to have originated from the quantities of a fish called "preñadilla" (_Pimelodus cyclopum_) discharged from its crater during one of its eruptions--a phenomenon which, after a searching investigation, was discredited by Wagner. Cayambe, or Cayembi, the second highest peak of the Ecuadorean Andes, has the noteworthy distinction of standing very nearly on the equator. Its base covers a large area, and its square top, rising far above the snow-line, is one of the sights of Quito. Antisana is crowned with a double dome, and is described as an extinct volcano, though Humboldt saw smoke issuing from it in 1802. On its western side is the famous _hacienda_ (farm) of Antisana, 13,306 ft. above the sea, where Humboldt resided for several months in 1802. Sara-Urcu stands south-east of Antisana in a densely forested region, drenched with rain and only slightly explored. Sincholagua and Rumiñagui are the next two peaks, going southward, and then the unrivalled cone of Cotopaxi (q.v.)--the highest active volcano in the world--from whose summit smoke curls upward unceasingly.