The Coeur d'Alene press. (Coeur d'Alene, Idaho) 1906-1907, 1907-07-15

Inc waters OF Uno &EeAS 4okoas
The investigation Of the quality of
the waters OF the great lakes, begHn by
the Unlted States geological survey
about nine months, ago, has reached a
point where interesting results are
available.
The object Of the WORT was to deter
mine the quality OF the waters carried
by the great lakes and the changes
that take place In their mineral con-
tents between the head Of Lake Su-
perior and st Lawrence river, For
this purpose samples OF water were
collected from each OF the lakes at reg
uIar intervals and shipped to the labo-
ratory OF the survey ut Washington for
mineral analysis. Says the government
report:
The analyses show that the waters hold
"a solution varying quantities OF calcium
and magnesium compounds which. from
their tendency to form scale or incrusta-
lions on boilers, are called inerustants,
Named In the order OF the total content
OF incrustants. beginning with the lowest,
the lakes rank az follows: Superior, HUI
E0Ut hktOMIkaut GAlAtANtQ anu 1G1t. Auc WA
ters OF Lake Michigan and Lake Huron
arc nearly identical In quality. and the
same may be said OF those OF Lake Onta-
rio and Erie Lake Superior however.
carries just about half the amount OF In
crustants borne by the other lakes.
The reason for this variation 10 found In
the geologic formations that surround the
lakes. The streams flowing into Lake Su-
pertor drain areas composed chiefly of
crystalline rocks, which yield scant guam
titles OF mineral matter to waters flowing
through them; the streams entering Lake
Michigan and Huron, on the other hand
traverse regions made up largely OF solu-
BILE nedimentRry rocks-limestones. sand
stones and elayB-whieh yield TO the VIA
ters comparatively large amounts Of the
calcium and magnesium compounds. The
difference In mineral content between
Lake Huron and Lake Michigan results
from the dilution OF the water OF Lake
Huron by the softer water Of Lake Supe-
rior. Lake Erie 10 highest In incrustanta
because Il receives not only the waters
from Lakes Michigan and Huron. but the
drainage from immense areas OF sedimen-
tAry rocks In Indiana and Ohio and in the
province OF Ontario. The waters OF Lake
Ontario are softer than those OF Lake
Erie because they have been diluted by
drainage from areas OF crystalline rocks
In New York and the Canadian province
The water Of all OF the lakes 10 modified
greatly by the large amount OF rain and
snow directly added to their surfaces
serving 20 meaaurably lower the proper
ton OF mineral matter. The quality OF
the water In each lake varies but little
from month to month; the variation H.
however. measurable. and In winter ths
mineral content - higher.
The lake water Is. as a rule. very
clear. containing practically no sus.
pended matter except in times Of
storms. when the sand and deposited
organic matter near the shore are STIR
red up by wave action. Il has beer
computed that more than 100000
tons Of mineral matter. chiefly calcium
compounds. held invislbly In solution
are annually carried from Lake Erie
20 Lake Ontario over Niagara falls
But Notwithstanding this enormous
amount OF dissolved material In thelI
waters the investigation proves con
cluslyely that as long a. the great
lakes remain unpOlluted by sewage
they will AFFORD the region surrounding
them the best available water supply
for municipal and lndnatEial ussa.