J. D. Dana— Volcanic Action. 107 
figure has been copied into several text-books. The hole may 
be what is left of a small lava pool after contraction from cool- 
ing. It varies greatly in size, from that of the open lava-pool 
to a diminutive hole through which drops of lava only a fourth 
of an inch in diameter are thrown out. One of the specimens 
which I obtained at the crater was a group of three slender 
columns, two to tkree inches apart, and about seven inches 
high, each made of lava drops of the small size mentioned—a 
fourth of an inch. Often the blow-hole emits intermittently 
only steam, whose rush out sustains the appropriateness of the 
name. Prof. Van Slyke describes one in action and ejecting 
lava, on page 96, and Mr. Dodge speaks of others, emitting 
steam only, on page 100. 
Rev. C. S. Stewart, at his second visit, in 1829, saw, as he 
states, four cones from a few feet to twenty in height project- 
ing flames [lava-jet] under a “laborious action of steam,” one 
of which, tapering almost to a point, had ‘been formed by suc- 
cessive slight overflowings of lavas which, as it rolled down, 
cooled into irregular flutings ornamented with rude drops and 
pendants ”—a good example of blow-hole action and result. 
9. Source of the vapors.—W hile part of the vapors, as is well 
understood, are from the same deep source as the lavas or from 
their constituents, and some water may be bere included, far 
the larger part have a more superficial source. The vapors 
from the deep-seated source of a conduit should vary little in 
amount except through variation in the area of liquid rock 
exposed ; and the same would be true if the lava were a fused 
sedimentary rock of the depths below. But in fact, the varia- 
tion between a time of quiet and of approaching eruption is 
often immense; the amount may increase rapidly as the height 
of the lava in the vent increases, proving that, as usually con- 
ceded, other more superficial sources of water-vapor exist. 
The more superficial source may be either, as is generally ad- 
thitted, the sea, or the fresh water of the land. Marine products 
like chlorides abundantly deposited about steaming fissures in 
the crater and outside, as at Vesuvius, have been accepted by 
most writers as evidence of the access of marine waters; and 
the absence nearly of such products at Kilauea, I regarded as 
evidence of the access there of terrestrial waters mainly. The 
latter are as likely to be concerned as the former, and the more 
so in most volcanic regions on account of the distance from 
the sea. 
The very abundant rains over eastern Hawaii, the bare cav- 
ernous lavas of the mountains, arranged partly in layers or 
streams, and partly in vertical dikes often radiate to the crater, 
and the freedom from water-courses over a large part of the 
eastern and southern slopes of Mt. Loa, led me to regard the 
