The Washington herald., 1921-11-07


Physics Club % the Bureau NJ
Standards. Bureau Of Standards,
this afternon. 4:3o O'Clock. Prof.
Henry Fielding Reed. of Johns
Hopkins University. will speak
on Cause Of Earthquakes"
SWING OF WATER IN FUNDY
BAY CAUSES GREAT TIDES.
The true cause Of the worlds
greatest tides in the Bay OF Fundy
has been found 20 be due 10 a
swinging Of the water in the bay
by the pull OF the moon, II. A. Mar
mer, OF the Coast and Geodetie Sur
vey. told the Philosophical Society
AZ its meeting at the Cosmos Club
Saturday night.
4 In the Bay OF Fundy there occur,
the greatest known rise ana far
of the tide" he said. "In the
npper part OF this bay the
tide twice each day rises ana
falls through a vertical distance
Of from forty TO fifty feet For
six hours the water rises ana IN.
following six hours IL falls; and
during this time there are periods
when the water rises or falls twelve
feet or more in one hour.
1T was believed until very re-
Gently that the great tide in this
bay was brought about by its shall
lowing bottom and funnel shape. Al
its mouth the bay is about 900 feet
deep and eighty miles wide, while
at its head it is reduced to a few
very small shallow streams. The
explanation given until recently was
that the tide wave coming in from
the ocean was cooped up as Il ad-
vanced up the bay. the tide rising
higher and higher as the channel
became narrower and shaIIower."
From recent studies. however. Il
has been found that the rise ana
fall Of the water in the Bay OF
Fundy behaves. not as IL a tide
wave entered from the ocean and
progressed upstream, but more like
the rocking Of the whole body OF
water in he bay like the alternate
swashing of water in a box from
one end to the other. II has been
found, too, that when the water
in any bay is disturbed, 81 rocks
from mouth TO head, the rise and
fall being very small at the mouth
but increasing gradually to the
head where the rise and fall is
greatest"
From experiments and also from
theoretteai conservation ~ mas
been discovered that the time taken
for the water in a bay TO rock
back and forth depends only on the
length Of the bay and on the depth
Of the water. and when these guam
titles are known for any bay the
time required for the water to os-
cillate back and forth can be cal
culated. Such a calculation for the
Bay Of Fundy gives for its period
about 1919 hours.
I'VE known from experience that
in pushing a child in a swing, a
slight force repeated az regular IN
tervals that coincide with the De
riod OF the swing will finally re-
suit in a very vigorous swinging
Just SO in the rocking OF the water
in bay, a slight force applied at
regular intervals that coincide with
the period Of oscillation Of the bav
will be sufficient to maintain
vigorous oscillation OF the water
in the hay. And in nature we have
such periodic force in the ocean
tides, the period OF which is about
12+ hours"
The cause OF the great tides in
the Bay Of Fundy is therefore found
in the fact that the period Of oscH-
lation Of the bay comedies with the
I period Of the tide Tho waters of,
the bay have been put into oscilIa-
ton by the disturbing force ~ thel
tide and since the period Of the,
tide comedies with the period Of,
oscillation Of the hay. this oscfIlat-
ing motion has finally reached IL
most vigorous stage. being steadiIvl
maintained by the ocean tido."