ALAJUELA AND THE VOLCANO POAS 357 



On the north side were a few faint streaks of greenish- 

 yellow. 



The bottom of this conical hole was occupied hy a lake of., 

 ashy water, in color and consistency like a huge bed of thin 

 mortar. Its surface was covered with a lighter gray scum, 

 which was blown by the wind into little ripples and streaks. 

 While we were there, there was no movement of the water 

 that seemed to be caused by forces within the lake or be- 

 neath. Except for the rippling of the scum the water was 

 perfectly still and placid. The sulphur smell was very strong 

 and there was much sulphur among the rocks near the water. 

 The trails down to the lake, always rough and dangerous 

 because of dislodged stones and slipping ashes, were almost 

 obliterated. There seemed to be absolutely no vegetation 

 within the crater itself. Two little flies, a beetle and 

 one butterfly were the only insects I saw while at the 

 crater. 



Some of the stones were quite large. We saw them as 

 much as two feet long and a little narrower (most of them 

 were slightly longer than wide) and some other visitors to 

 the volcano, who walked about more than we did, told us 

 of seeing stones a meter and a half long (four and a half feet) 

 and half buried in the ash. Here and there were irregular 

 holes in the ash, varying in diameter and often half choked, 

 which have served as chimneys or additional outlets for the 

 gases of the volcano. The usual outlet is supposed to be a 

 similar but immensely larger chimney below the surface of 

 the lake and the escape of the gases through the waters of 

 the lake, accompanied by the steam formed under pressure 

 from the water percolating down the chimney, causes the 

 geyser-like eruption. 



In addition to this present crater with its ashy lake, Poas has 

 another crater-lake higher up on the mountain, whose water 

 is normally sweet and clear. We were told that the ash 



