1880. } The Island of Dominica. 769 
as by the considerable increase in volume incident thereto, heat is 
produced. In several instances, where the same changes were 
going on in rocks containing oligoclase, we have found thermal 
springs in the immediate vicinity. While decomposition of 
pyrite is more rapid, it does not extend so far from the surface 
-into the rocks as that of the feldspar. In connection herewith it 
may be mentioned that the waters of Wotten Waven hold an 
exceptionally large amount of alumina in solution. In spite of 
the diminutive size of the majority of the geysers, the quantity 
of water delivered is considerable. As it nearly all flows off, a 
very large supply must be furnished by percolation, or by entrance 
through fissures and along subterranean watercourses. 
On January 4, 1880, the inhabitants of Roseau had cause to 
feel somewhat alarmed. Taking into consideration the myste- 
rious legends as to volcanic-activity on the island, it will readily 
be understood that the appearance of a huge, dark cloud over the 
town shortly before noon of a clear day, might awaken some 
apprehensions. More so, however, when that cloud began to “rain 
down” fine particles of gray, mineral-like material which soon 
changed the green foliage of all vegetation to its own color. 
Pompeii and Herculaneum saw the initiation of their destruction 
ina similar cloud. So far as could be determined by cool obser- 
vers, among whom Dr. Nichols of Roseau was prominent, the 
cloud extended for a distance of about eight miles beyond the 
town and then was lost, going seaward. Even in the latter part 
of February the finely divided “ash” could be found on many 
plants. It consisted of very minute fragments of trachytic rock 
and small crystals and particles of pyrite. The general impres- 
sion was that a volcanic eruption had taken place at, “ Boiling 
Neither definite detonations were heard nor seismic disturb- 
ances felt by the more critical observers. A low rumbling noise 
Seems to have preceded the appearance of the cloud. Several 
venturesome explorers determined to investigate matters, but 
were obliged to return without results, as all access to the lake © 
had been barred by dislodged rocks and earth. During our stay 
at Roseau a party was organized to visit the lake, and a new road : 
was cut through the forest. Numerous colored attendants, whose 
climbing qualities and endurance we could not but admire, trans- 
ported baggage and provisions. Reaching a point several miles 
t 
