The Hawaiian gazette., 1882-11-15

Capt. E. c. button, U. S. A., delivered lecture
at the Music Hall last evening under the auspices
OF the Honolulu Library Association. A large and
| appreciative audience was present, including His
Majesty. The lecturer received the weIl-merited
| applause Of those present. Following Is an alb
stEact OF Capt. buttons lecture:
The rivers Of the Atlantic States, like the Had-
son, Delaware, Susquehanna and Potomac, have
their sources far inland at elevations Of only few
hundred feet. In order to rea.h the sea, they
pass through ridge after ridge Of The AppalEchians,
IN aeep narrow gorgts- How were these gorges
formed which are 50 convenient for the passage Of
the streams and seemingly designed for them7
The phenomenon of rivers cutting through mount
aims and lofty plateaus instead OF going around
them is common in all great rivers Of the world.
Pethaps the most extraordinary instance Is the
Colorado river Of the West.
The Colorado is only an extreme illustration Of a
fact disclosed by majority Thought not by all
| OF the great rivers of the world. They do not
| avoid mountain ranges or high plateauS which lie
athwart their tracts but cut through them in pro-
found gorges or canons How were these great
| pathways OF the rivers excavated? What power
has opened these chasms to allow the rivers to
pass Tothis question geology gives as a COM
plete and convincing answer which appears when
We come to analyse two propositions The first is
that rivers cut and maintain their own channels
The second is that those rivers which cut through
mountain ranges and plateaus existed before those
mountains and piatea1s were reared.
persOn examining the rivers Of the Atlantic
States would see no reason to believe that they
right. Those rivers have accomplished their work
and have cut down their channels 50 far that they
can cut no more. But in the West the truth Is
quite otherwise Excepting the lower portion of
the Sacramento and San Joaquin all the Western
rivers are cutting down their beds.
The tools with which the river works are the
sand and grit suspended in its waters Its action
IS identical in principle with the well know instru-
ment called the sand blast. Under favorable con-
ditions this action becomes very rapid and ener-
getlc. In one of the hydraulic mines of California
the escaping waters cut into basaltic bed rock at
the rate of Is feet per annum.
The quantity of debris which a river carries is
called its " load" Its ability to carry sediments
IS termed its transporting power" This power
depends chiefly upon the velocity of the stream
and the velocity again depends upon the declivity
of its bed. Where the eclivity is great tie veloc
ity and consequent transporting power are also
great and the bedrock is Kept bare and subject to
the grinding action Of the sand-blast. Where the
declivity is small the velocity and transporting
power are small sediment is dropped or forms
protecting cover 10 the bottom.
All rivers tend to the establishment of an exact
adjustment OF the transporting power to load. 1t
does this by cutting down its declivty everywhere
until the velocity and transporting power are SO
reduced that they begin to drop sediment on the
bottom and protect it from further wear. When
TINS stage IS reached the rivers grade tif not sub
lect to external disturbancel is in stable equili-
brlum and persists without change. Many rivers
have reached this condition; notably the Hudson
and Mississippi. 1t is termed the condition of
base-leyel.
Causes sometimes intervene to disturb base
level after it has been established. For instance
suppose the land along its course to rise. This
increases the declivty increases the velocity; in
creases the transporting power The river re-
sumes its work of cutting down its bed until the
lost equilibrium is restored. Or suppose the land
TO sink The declivity is diminished the velocity
and transporting lower reduced and more sedi-
ment is deposited building up the bed 10 the re-
quired declivity until base level is again attained
The Eastern rivers are either in the stage of
base level or very near it. But Western rivers
are far from it. In the West the decivties of the
channels are very great Consequently the bed
rocks are bare and the turbid waters grind
them with power which is evident TO the most
careless observer. The cause of the difference be
tween the Eastern and Western rivers is soon
stated. The Eastern country is an old region
geologically and has been but little disturbed in
recent periods. The Western country has until
the most recent epoch been a rising country thus
keeping up the declivities and giving the rivers
more and more work to do.
The speaker then proceeded to apply this beau
tful theorem to some of the active rivers notably
the Colorado showing that the rise of a mountain
range or plateau only provokes river to attack it
and cleave the mountain asunder and thus main
tain its right of way. Other applications were
gwen. One the striking thoughts deduced was
the antiquity of the great rivers of a continent.
They are older than the mountains or high plat
eaus; indeed among the oldest of its topographic
features. Amid all changes they alone have re-
manned with comparatively little change.