+ 
772 The Island of Dominica. [ November, 
trachyte. ‘ The reduction of the latter in size was purely mechani- 
cal, largely due to attrition, although certainly the force producing 
it was owing to causes entirely different. We estimated the area 
thus razed, of timber, at about nine square miles, and the average 
thickness of deposited lithological material at eighteen inches. 
Allowing for the fact that the latter was not densely packed, this 
estimate furnishes a total amount of more than 27,000,000 tons 
which had been removed from their normal position by catastro- 
phic action. 
As to the causes which produced the “ eruption,” the evidence 
on hand is sufficient to arrive at some conclusions. First of all, 
the idea of volcanic eruption must be dismissed. No grounds for 
-such assumption can be found, and the immediate vicinity of the 
scene of action exhibits no trace thereof. On the other hand, the 
decomposition of pyrite and associated minerals is here the evi- 
dent source of heat. Water is plentifully supplied by precipita- 
tion as well as by superficial and subterranean drainage. If we 
can assume, and it seems reasonable that we should, that either 
the supply of heat-producing material had increased without 
` adequate vents for accumulating pressure being in existence, Or 
that the vents, at the time acting as safety valves, were by some 
means reduced in area of cross-section, then, necessarily, an 
explosion must follow as-soon as the pressure of steam and gases 
is able to overcome superincumbent weight. Added to this we 
have learned that decided barometric disturbances were observed 
on Dominica at atime immediately preceding the catastrophy. 
In case a bare equilibrium were maintained, certain changes of 
atmospheric pressure alone might account for a sudden release of 
gases under pressure. Every indication speaks for the assump- 
tion that the phenomenon is to be regarded as an explosion and 
not as an eruption, so far as the latter pertains to vulcanicity. 
In the course of a few years the damages so suddenly wrought 
_ will have been repaired again. Plant life in this climate is vigor 
ous, and it will seem but a short time ere the now barren slopes 
will once more be clothed in green. Nothing will remain but — a 
‘some scarred veterans to tell the tale of the disastrous explosion 
of 1880. Although a repetition of such occurrences may- 
looked for, the area is too limited and the seat of disturbing 
chemical action too superficial to endanger the safety of Do- — = 
minica. 
