Daily Kennebec journal. [microfilm reel] (Augusta, Me.) 1870-1975, 1912-01-25

determined by temperature studies at
| various depths, from the surface down
! To the bottom, maoe largely under the
/ direction of and with an instrument
| invented by Prof. George c, Whipplc,
| who is now at the head ot the new
/ department of sanitary engineering in
the Harvard Graduate school of APP
| piled Science. And in this connection
! it is not without interest that tn" first
! class in Prof Whipplc's new depart
mcnt mas this fan tested the waters
| of Lake Coehituate taking samples
| for bacterial and chemical analysis,
and determining temperatures at diff
ferent depths with tine Interruptions.
which is essentially the invention of
, Prof. Whipple made when he began
the first really modern scientific en-
animation of the Boston water sup
ply, at Chestnut Hill reservoir, in 1NS9.
The thermophoue is one Of til" most
Interesting of scientific Instruments.
as anyone will agree Who has seen an
observer taking the temperature Of the
water hundred feet below the bet
tom Of his boat by turning the dial
knob on a small box which rests on
his knees while he holds an ordinary
telephone receiver to his ear. Tho
principle of the thing rests on the fact
that the resistance of metals u the
pass &c of an electric current varies
with the temperature of the metals.
An Insulated cable "a very slender ca :
bic. of course1 With 4 coil formed Of
TIVE metals on its lower end is drop
pei into the water To Il determined
depth. and then Il current is sent
through from small battery in the
box in the boat Tic three wires of
tho cable are attached to the posts OF
what is known 10 electrical students
is Whcatstonc bridge. while the tel
4phonc receiver is also put in circuit.
By turning the Indicator, which varies
a part of the Resistance iii the circuits,
the observer finds 4 point GA his tent
perature dial where there is no sound
from the telephone receiver, and this
silent point corresponds To A certain
temperature. Before the thermophone
was invented the apparatus for taxi
ing underwater temperatures WAS
slow in operation. and not very aeeu-
rate. even with careful handling. With
the thermophene. temperatures aecu-
rate within a tenth OF a degree Fahr
can be taken with one minutes in-
mersion OF the coil 1t the desired
depth.
Lake CoehitGate Is 50 feet deep The
temperature at the bottom during the
winter. when the surface is frozen, is
not far from the temperature of MAXI
mum density of water namely S9.2
deg. Fahr.r The heaviest water is at
the bottom. the lightest At the top
and the intermediate layers are ar
ranged according u their density,
which depends on their relative tenn
peratares With these conditions the
water is in comparatively stable eqai-
librium; it is "inversely stratitied."
This is the condition during the win
ter stagnation, which has not begun
this year because Of the high winds
which tend to mix Up tile water. and
the absence of Ice, whic! permits this
wind mixing.
As soon as the ice breaks up in the
spring the surface water begins to
grow warmer. As It approaches the
temperature Of maximum density, 1913
deg. Fair. II grows more dense as it
gets WarMer.s and a il becomes dens
er it begins To sink. Thus until the wa
ter has reached the maximum density
temperature from top to bottom there
is a mixing Of the waters. aided by
wind action on the surface. This is
the spring circulation" or tho spring
overturning' lasting several weeks.
As the season advances the surface
water becomes warmer than that at
the bottom, and consequently less
dense, or lighter" In this period
the effects Of change Of temperature
at the surface and wind effects are
not sufficient to mix the waters, and
there results the long summer stag
nation" During this period the dens-
est water is at the bottom, and the
water is directly stratified" up to
the least dense at the top. From
April to November the bottom tenn
perature remains practically the same,
and the water below a depth of about
% feet remains stagnant. In the
autumn the surface Goods, and when
the temperature is substantially the
same from top to bottom, The whole
mass Of water is in unstable cquili-
brium. winds have great effect, and
there comes the great oVerturuing."
and all the water is in circulation.
| In December. usually, the lake freezes
and the winter stagnatiou' begins.
Temperature variations, are more
| important than they might at first
seem, and this Importance has been
disclosed By "sampline' the water at
various depths. just as the tempera-
! ture is taken at different levels. The
samples of water are examined for
bacteria, for other microscopic plants
and for animals, and are analysed to
determine their chemical character
. From all these examinations it is pos
sible to construct a cross section of a
/ lake or reservoir, showing tire pre-
else condition and quality of the
water at any humber Of levels This
/ is no place to go into the extremely
complicated system OF physical, chem
| ical and microscopic examinations
which determine the fitness of The
water for drinking. but one or two
very significant items can be men
toned briefly, The so-called self
publication" of wrater depends on tn,
dissolved oxygen it contains about