196 HAWAIIAN ISLANDS. 
the vast area, till the rising bottom plain became as high as the black 
ledge; still the pools boiled on, and, as always happens, with increased 
activity, owing to the augmented pressure and the greater height of 
the column of lavas through which the steam and gases make their 
way in order to escape; the black ledge is finally flooded, and the 
accumulation reaches the maximum which the sides of the mountain 
can bear. The pressure, aided by internal forces from vapours, which 
had increased with the increased activity and area of action, conse- 
quently breaks a way out for the molten rock. In some cases, on the 
side of the island where the escape takes place, the first indication of 
the eruption is the approach of the flowing lavas. We would not imply 
that the land is proof against earthquakes, for slight shocks not unfre- 
quently happen, and they have been of considerable force during an 
eruption. But earthquakes are no necessary attendant on an outbreak » 
of Kilauea. It is a simple bursting or rupture of the mountain from 
pressure, and the disruptive force of vapours, in consequence of which 
the mountain, thus tapped, discharges itself. 
The eruption of 1840, must have been small compared with that of 
1823, when the stream which entered the sea was “five toeight miles 
wide.” ‘The plan of the crater after the eruption, made by Lieutenant 
Malden (page 185), gives an area for the lower pit of full 65,000,000 of 
square feet, nearly double the extent it had when surveyed by the Ex- 
pedition ; and allowing four hundred feet for the depth, as determined 
at the time by Lieutenant Malden, the amount of the lavas of the 
eruption would be 27,000,000,000 of cubic feet. 
Ill. Nature of the outbreak.—The lavas, it appears, found exit by 
a series of rents through the sides of the mountain. It was nota single 
opening and an outflow, nor a single continuous fissure; but a series 
of fissures at intervals, through which the lavas rose to the surface. 
The first fissures were small, and but little lava escaped, and from 
some, only steam; through the last twelve miles there were several 
rents, two or three in some places running nearly parallel; and the 
tufa hills mark the position of three where they reached the sea. 
The beds of sand over the strearn of lava, and the sandhills of the 
seashore, show us that tufas, and the lavas they cover, may be, in some 
instances, of simultaneous formation; and also that it is possible that 
tufa beds may intervene between different layers of lava, and all be- 
long to the same period of eruption. 
In some descriptions of the eruption of 1840, it has been implied 
that the lavas, after reaching the surface, at times disappeared be- 
neath, then broke oat again, and so flowed onward to the sea. ‘The 
