416 PACIFIC OCEAN. 
A third undoubted example is before us in the Ladrones. For in 
these islands the same evidences of long extinction of the fires are ap- 
parent in the southern islands, while to the north, these indications gra- 
dually disappear, and at the northern extremity of the range, the fires 
still burn. The smaller size of the northern islands is no proof of 
their more recent origin, but rather of a longer continued subsidence. 
We cannot judge of the actual size and extent of a volcanic mountain 
by the part above the water, any more than we can decide upon the 
length of a line from the size of the buoy attached to it. 
The Society Islands require farther examination before we can 
confidently state their relation to the system. ‘This is the case also 
with regard to the New Hebrides, which have been but little ex- 
plored. 
2. The fissures of a range may constitute 
a. A single line or “continued” sertes. 
b. An “advancing” or “receding” series, the successive parts lying 
somewhat to one side of each other, though having a common direction. 
c. A compound series, including several parallel lines, and in either 
case there are often 
d. Other transverse lines at right angles, or nearly so, to the prevalent 
trend of the group. 
In figures of Australian dikes beyond, we have represented in- 
stances of the overlapping of the successive parts — a common 
feature of fissures.* Among the Pacific groups, this point is 
fully illustrated. In the long Hawaiian chain, the successive parts 
evidently recede, as we trace the line from the west eastward, each 
being a little to the northeast of the preceding. The lines inclosing 
the chain on the Pacific chart, are drawn so as to show this feature 
of the group. We cannot, of course, point out the exact courses 
of all the various fissures that were opened when the islands began ; 
but we may discover enough to convince us of the general fact al- 
luded to. In the eastern portion of the chain, where, as we have 
remarked, the rupturing was greatest in amount, we observe the two 
* Upon this point we can refer to no more valuable work than the Report by Dr. J. G. 
Percival on the Geology of Connecticut, (8vo. New Haven, 1842,) where the numerous 
trap dikes of the state are laid down with minute accuracy of detail. The able author 
points out the different kinds of series in the lines of dikes, the “ continued,” where the 
several linear rents form a continued series in the same line as well as direction; and 
“< receding” or “ advancing” series, where they have a common direction, but the suc- 
cessive parts have a position a little behind or in advance of one another. See also Am, 
Journ. Sci, li. ser. 11. 390. 
