The Washington times., 1901-07-28
MEASURING RIVER POWER.
Recent Scientific Work in the
Eastern Part of Maine.
Summer Training for the students
of the Massachusetts Institute of
Technology Speed of Flow and
Quantity of Water ReckOncd.

MACHIAS, Me-. July pa number
of students from the Massachusetts In
stitute of Technology have been a
work this summer determining the vol
ume of water and rate of current OF
the Machias River. which flows dowr
through Washington County-the east
ernmost county in the United States
and empties into the sea not far from
Eastport. In many ways the expert
ments illustrated some little known
problems of hydraulic engineering with
unusual fullness-perhaps more fully
than would be the case in work under
taken for a directly practical end. The
measurement of the flow of a stream
is one of the most important as well
as one of the most difficult tasks that
the hydraulic engineer has to encoun-
ter. Not only is this work all-essential
in deciding upon the sources of mu-
nicipal water supply, but the effective
ness of the hundreds of plants through
out the country which depend on water
as their sole or chief source of power
can be guaranteed only by his skill and
observation, since ii is obvious that if
there should not be enough water or II
the water failed to move fast enough
that is, did not have sufficient pitch
the water wheels simply would not
turn. Or. if there is doubt or ignor-
ance of the conditions, the full power
of the stream may not be utilized and
a portion of the capital engaged will
thus be employed to no purpose what
ever. At the present time, especially,
the value of water power has SO in
creased since it was made possible to
carry an electric current long distances,
that exact knowledge of the possible
power in a given privilege has be-
come industrially matter of the
very first Importance.
In solving such problems the engineer
has to consider variety of factors-the
cost and nature of a dam, the height
and character of the banks, the dis
tance of the back water'-the length,
that is, of the level mill pond which
stretches from the dam back to the
stream again which in turn gives him
the full amount of ''fiowage" or damage
which will be caused by the overflow
into the riparian" or adjacent lands.
There is always, too, the important
question Of the general character of the
river, as it may be called-whether it is
good with an even flow of water the
year round. or bad because subject
to sudden rises from spring fires hets or
falls from summer droughts; SO that
before the engineer is through with his
study of a water privilege, or a site for
ton, he must have called into use his
knowledge of typographical surveying.
of climatoiogy, of forestry, and of me-
teorology.
The institute students, however, have
devoted their time in Machias to a de-
termination of the basic factor upon
which all the others rest-the flow of
the river. Though the actual measure
ment of the rate of flow is made by
floats, or by current meters, as they
are called, the first thing done in get
ting at the flow as whole is to OBJ
tain the cross section of the river at
certain points. Marks in line--range
points" or ''sights''-are set up on the
bank, two on each side in tandem, so
with the back sight the observer is
on the established line. The boat from
which the soundings are taken is held
in position while they are made. The
position of the boat, which would give
the distance from the shore, is found
by taking angles with a sextant to
points on the banks. which are at ex-
actiy known distances apart, or by
angles taken from two points on the
shore to the boat after which, by the
old geometrical formula of given one
side and two angles of a triangle to
determine the other side" the boats
precise position in the stream is easily
reckoned. These soundings are made
across the river at short intervals until
a plan may be drawn which gives an
irregular lower line-the bed of river
with a straight line at the top for the
water level. This is reduced to a reg
ular figure of so many square feet, so
that when it is found how fast the
water moves it is easy to know how
the cross section of stream reduces
to LOCO square feet and the water moves
at the rate of a foot a second, in one
second 1000 cubic feet would move by.
or 5000 cubic feet a minute
To find out how fast the water moves
two methods are used. In the first a
float or floats are employed. For ap-
proximate calculations a single float is
allowed to be carried down by the
stream. Where ii is narrow enough
strings are stretched across and the
time the float takes in passing these
is noted. but on large rivers and for
more exact work a telescope with cross
hairs in the field is placed on one bank
and sighted at mark or range" on
the other. and the float is timed as it
passes vertical cross hair. Where it
is desired, in addition, to eliminate the
influence of the wind and waves, two
floats are used-one attached to the
other. The upper and smaller of the
two pieces floats on the surface and is
used only as marker" the larger
one Is submerged by weighting so that
it may come down stream at the real
rate OF the current uninfiuenced by the
surface agitations which retard or ac-
celerate the speed Of the marker itself
When floats are used a number of |
cross sections must have been figured |
out. SO that an average cross section |
for the distance travelled may be es-
tablished, but where a current meter
the second method of determining the |
speed OF fow-is used only one cross |
section is needed The rnater &c potbip,,