Evening star., 1915-12-12

under it hundreds of county demon
stration agents in all parts of the coun-
try An important element of the pres
ent movement will be an intensive test
through the demonstration agents of
selected programs of films in FIVE
states. From these tests suggestions
will be gotten for improvements in ex-
listing films and new subjects needed.
On the tests. il is believed, will hinge
to a large extent. the committees de-
cisions on questions it has been con-
siderinG for some time, such as the
advisa bility of the states relations
service making films of its own for use
through its country wide organization,
sale of films by the department to agri-
cultural colleges, and. most important
of all. release of the departments edu-
cational subjects through the national
commercial film exchanges that would
show them in thousands of 1heaters
throughout the country.
Most lakes rise and fall and empty
themselves as the rainfall dictates, but
in Panama, where Uncle
Panama Sam took liberties with
nature in many ways,
'' even to creating the
greatest of artificial lakes rainfall and
most other activities of nature are han
died or curbed by machinery as the en-
gineers wish.
Just how much water it would be
necessary to handle to keep the lake at
a desired height was carefully calculat-
ed before the age-old valleys of the
isthmus were turned into lake bottom
and the hilltops into islands, and dams
and spllways were constructed accord
lingly The most crucial test that the
works have ever had came in the last
few weeks when the heaviest downpour
of rain and the Sharpest rises in the
isthmian streams that have occurred
since the opening of the canal We're
experienced.
The tropical doWnpour continued for
the better part of two days and two
nights and the great volume of water
tended to raise the 164 square miles of
lake surface rapidly. One after an
other, however, the spillway gates in
the Gatun dam We're put in operation
until for nearly eight hours six were
discharging simultaneously. Approx
mately 1000 cubic feet of water rush
ed through the gates at each tick of a
watch-euough to cover two acres OF
ground almost a foot deep. In TINS way
the great lake was kept practically at
the level that would have been main
tanned if no rain had fallen. As the
rises spent themselves the splilWay
gates were closed one by one until a
single aperture was emptying the nor
NAL inward flow of the streams.
=
procedure of keeping the lake at the
level the engineers had decided upon
was that the operations We're per
formed by electricity generated by the
very water that was beng controlled-
The electric generating plant for the
Canal Zone is situated at the Gatun
spillway, and it was portion of the
power produced there that was used to
open and close the great gates, as a
greater or less flow was desired. 1t
hi fn n
before the waters actually began TO
rise at the dam. for the operators in
charge of the gates received messages
telling of water levels from sauging
stations along the Chagres river and
at various locations along the lake
shore.
During a forty-two-hour period it is
estimated that nearly 0o,00o,ooO cubic
feet of water was allowed to pass
through the gates-enough to cover
an area of 500 square miles half a
foot deep and so create a large lake
OF its own.
During the month of October, one of
the rainiest months of the rainy sea :
son. more than seventeen inches of
rain fell over the 1920 square miles
that make up the drainage area of the
lake. This quantity of water would
cover the state of Delaware practically
ten inches deep and though some
evaporated from the lake surface, prac-
tca1ly none passed through the locks
since the canal was closed. 1t was
necessary. therefore. to pass most of
il through the Gatun spillway gates,
in order to maintain the eighty five
foot level.
With the advent of the dry season
this month. the engineers in charge are
reversing their procedure and will
keep the gates closed until the lake is
brought UP to the eighty-seven-f foot
level. since surplus of water viii
be necessary to operate the canal and
the electric plant during the period of
little rainfall and much evaporation