356 A YEAR OF COSTA RICAN NATURAL HISTORY 



not scorched by the ashes but their leaves when rubbed 

 clean looked green and fresh. Evidently the ash was not 

 hot when it fell upon them, but the amount was quite suffi- 

 cient to choke the leaves. In these upper woods I saw just 

 one insect, a large fly, and we heard one bird. Mr. Clark 

 said that usually there were many birds and insects and 

 probably the presence of the ashes on the trees had driven 

 them away. 



We came out on the edge of the crater, on the south side, 

 about 9.30 A. M. The mountain was then entirely clear and 

 we had an uninterrupted view although there were clouds 

 near and before we left the crater was mist-filled. 



Between the edge of the woods and the beginning of the 

 slope down into the crater was a bare, rocky, ash-strewn 

 slope five or six feet wide, often less. Poas has been called 

 the world's largest geyser and its crater has the shape of an 

 inverted cone. Although its exact dimensions are not known, 

 the diameter of its upper opening has been estimated at about 

 a kilometer (five-eighths of a mile) and its depth, to the sur- 

 face of the lake within, at about three hundred meters (or 

 nine hundred and ninety feet). The figures given by the 

 Costa Rican Commission of 1910 for the area of the lake, 

 fifteen hectares (or thirty-seven acres), imply a greater 

 diameter than the one hundred and fifty meters (four hun- 

 dred and ninety-two feet) which Sapper considered it to 

 possess in 1899. The sides were deeply scored and gullied 

 by the force of the ash-laden streams that rush down them 

 after an eruption, particularly the recent one in which the 

 ash was vastly more abundant than usual. Formerly the 

 sides showed horizontal strata of varying colors and (to 

 judge from the photographs) sharp outlines, but at this 

 time the horizontal banding had almost disappeared, while 

 the grayish white ash streams had rounded the edges, cut 

 fresh gullys and modelled the sides with vertical scorings. 



