BOILING LAKE OF DOMINICA 571 



time of the author's visit (April 5, 1903), show that the lake stands at higher levels 

 during rainy seasons, with corresponding increase in diameter. Two small streams 

 of cool water flow into the basin from the north-northwest, while a single stream 

 discharges the overflow of the pool toward the south-southeast. 



There are two centers of ebullition, one of gentle action in the northeastern quar- 

 ter of the pool and one of great vigor in the western third. Over the latter the 

 water rises in a dome about 2 feet higher than the general level of the lake, and 

 occasional jets throw water 5 or 6 feet into the air. The quantity of water ordi- 

 narily rising through the two conduits indicated by the centers of ebullition seems 

 to be rather small, judging from a comparison between volumes of the inflowing 

 and outflowing streams. It probably varies with the seasons. 



The gas rising from the Boiling lake is mostly water vapor (steam), which must 

 have a temperature of fully 100 degrees Centigrade at the vents, since the temper- 

 ature of the brook leaving the pool is 87 degrees to 88 degrees Centigrade, as 

 determined by Sapper. A strong odor of sulphur gas (seemingly H 2 S) pervades 

 the steam. The water of the lake is bluish milky white fram the particles of pre- 

 cipitated sulphur which it carries in suspension. Carbon dioxide also seems to be 

 present in the discharge from the vents, to judge from the death by asphyxiation 

 of the Englishman, Mr Give, and his porter on the border of the pool in Decem- 

 ber, 1901. Sometimes, according to Matson Rolle, the guide, when the lake is very 

 full, the strong boiling ceases and bubbles of gas and steam rise copiously from all 

 parts of the lake. On days when such conditions prevail the lake is particularly 

 dangerous to approach. 



The basin has been formed by the action of the fumaroles and spring water, in 

 conjunction with the surface water, undermining and removing the slide rock and 

 debris from the mountain. Mud is thrown out occasionally from the lake, but the 

 walls of the basin seem to have been built up by ejected materials. Matson Rolle- 

 and other residents of the colony state that during exceptionally dry seasons the 

 streams disappear and the basin is empty, except for periodic inflows through the 

 fumarolic vents in its bottom. The basin, therefore, is shallow, a fact that was 

 indicated also by the shape of that part of the bottom visible at the time of the 

 author's visit. The walls of the basin rise about 15 feet above the water at the* 

 outlet, about 60 feet on the west side of the pool, and somewhat higher on the east 

 side. They are vertical or nearly vertical, but the borders of the pool can be easily 

 attained along either the inflowing or outflowing stream. 



The intermittent rising and falling of water in the conduits during times when 

 the basin is dry, observed by Mr Bell, administrator of the colony, and reported 

 by Sapper, points toward geyser action, but the fountain-like discharge of typical 

 geysers is absent. 



The paper was illustrated by means oflantern slides. 



The three papers by Doctor Hovey were discussed as one by Angelo 

 Heilprin, I. C. Russell, and the author. 



LXXI— Bull. Geol. Soc. Am., Vol. 16, iy<)4 



