a a 
Pte ner es 
—— TF ae 
J. D. Dana on Denudation in the Pacific. 61 
plunging down heights with frightful velocities, and then the 
power of the stream would not be disputed.* 
But if the waters have been thus efficient in causing denuda- 
tion and opening valleys, may not fissures or dikes have deter- 
mined their courses?) The only test of truth, an appeal to facts, 
may answer the question. Mount Loa is a mountain yet un- 
changed. It has its dikes in great numbers: but over these dikes 
the country is more apt to be ‘raised a little from the overflow of 
lavas than depressed, and this would turn off the water. Again, 
we see no instances of dikes yielding, and offering a course for a 
Stream. As to unfilled fissures, there are few of them, aud these, 
With rare exceptions, are immediately about the active vents. _ Is 
either supposition then sustained by the facts presented? We 
know the tendency of water to take the lowest parts of a-snrface, 
and will it not follow these parts, whether or not there be a dike 
or fissure? It is obvious that whatever ravines or depressious the 
floods of lava may have left, would be the courses of the waters ; 
and these depressions sas be followed to the sea, and ultimately 
become valleys. We may believe that the waters would not 
wait till there was a convenient fissure; they would go where 
tmcelination led, and make valleys with little difficulty, if there 
Were no guiding or aiding fissures. Were the dikes filled by a 
tock more decomposable or more easily eroded than those en-_ 
closing it, as is the case in some granitic regions, we should ex- 
pect that they would frequeutly become water courses: but this 
is seldom the fact in the Pacific islands. 
The valleys in some of the Canary Islands, extend from the 
Shores part way to the summit, as on Mount Kea and Hale-a-kala, 
and Sranauy for the reason alread y explained. We can detect 
se of the streams, from the rains of the mountains, is often so rapid that 
in some instances, the native villages ra Amy coast become flooded, before they have 
time even to move their pro perty.— erald. xxiii, 207. 
an, who has often peedonee the. coast of Hawaii, north of Hilo, and during 
the drier cae (which ver, are of short duration on this, the windward 
Coast,) fords the sldlont Banca without difficulty, gives the fo slowing account of 
his jo por a Sabri ga time of rains. “Great and conned ra. — fell during my ab- 
the numerous rivers became so swollen an hat the Pgh sight me 
them’ “9 fearful. These raging streams crossed my path ‘about 0 once in half a mile 
a distance of about thirty miles, and I was com led ta weap to Pag aca 
me. Most il 
ost of t 
course ave numerous cataracts from ten to a hundred pot fifty feet in hse 
dicular Though the torrents were so fearful as to make one almost quail 
at the t Co of strugg pling | with their fury, ropes were provided, and several men 
employed for the adve us task. plow apo a 2 ipo of aa, and 
energy and Be ‘effort, ess : n one’s grasp 0 rope, 
and buffet with the foaming flood. We at last ts th though at ston peril. 
At one of the rivers, we spent ae hue in pyle ie oa e we tA with 
any degree of rage extend our co ara i. I party t to the a 
Site bank. The streams are at s the bettie glee ravines, the banks 
pris ‘rey tn and often perpendicular bluffs of Semitic pen "— Miss. Her. 
