278 Mr. J. W. Mallet. On a Second Case of the [Mar. 6, 



January, 1886, began its eruption, and it continued in eruption till 

 November of the same year." 



The volcano in question — about 16,500 feet in height — is one of the 

 great mountains of the Eastern Cordillera of Ecuador, lying some 50 

 or 60 miles south and a little east of Cotopaxi, in between 1° and 2° 

 of south latitude, and about 85 or 90 miles in a direct line from 

 Guayaquil on the coast of the Pacific, where the specimen of ash was 

 collected. The appearance of the regular cone-shaped summit, rising 

 directly from a plain of only 5700 feet above sea level, is described as 

 very striking, crowned with perpetual snow, and resembling in aspect 

 Cotopaxi. Yillavicencio in his work on Ecuador thus speaks of it — 

 " JEsta bellisima montana estd collocada d un nivel inferior de todas las 

 otras montanas del Ecuador, la que hace que su altura aparente, mirada 

 desde su base, sea mucho mayor que la del Chimborazo. . . . Este 

 volcan tiene la figura de un cono perfecto, cuya parte superior estd 

 cubierta de nieves sempiternas que forman una especie de capucha la 

 que, contrastando con las negras penolerias de su base i algunos bosques, 

 le dan un aspecto sublime i bello : su descenso es rdpido por todas partes, 

 escepto por el lado en que se une con la cordillera, por cuya parte se puede 

 subir hasta principiar las nieves; pero de alii en adelante hay obstdculos 

 para el viajero mas intre'pido. La nieve deshecha de su copa se precipita 

 en cascadas elevadi'simas, que aumentanla hermosurade ese sublime cono, 

 que tiene de notable el encontrarse en el todos los climas, desde el frio de 

 la Siberia, que comienza en el limit e de sus nieves, Jiasta el de 27° del 

 centigrado que tiene su base." 



The most notable eruption recorded was that of 1777. The mountain 

 was long classed with apagados or extinct volcanoes, although from 

 time to time during the last century several explorers have reported 

 " smoke " as seen issuing from the summit. It is generally believed 

 in the surrounding country that a subterranean communication, 

 following the line of the Andes, exists between this volcano and 

 Cotopaxi, the one showing signs of activity when the other is in 

 eruption, and becoming quiet when such eruption ceases. 



The specimen of Tunguragua volcanic ash received by me had very 

 much the same appearance as that of the Cotopaxi ash formerly 

 examined — a very finely divided powder, of light brownish-grey or 

 fawn colour, a little lighter in shade than the Cotopaxi specimen. 

 Under the microscope the same minute grains and spiculee were seen, 

 having for the most part sharp, splintery edges and angles. The 

 same general mineralogical character was observed — essentially the 

 debris of trachytic " andesite " — with apparently less difference in the 

 colour of the felspar present, which was almost all white or colourless, 

 and with fewer disseminated particles of magnetite and specular iron. 

 There were some scales of what was probably comminuted vesicular 

 pumice. 



