Evening star., 1901-08-24
RAINFALL AND COMFORT
ATMOSPHERE MAY BE TOO DRY or
roo MOIST FOR HEALTH.
Calculation as to the Evaporation of
Water in American Lakes
and Rivers.
From the London tontario, Advertiser.

1
Few natural phenomena are of greater
practical Importance than rainfall and
| evaporation. They concern closely both
our health and our personal comfort. An
| arid condition OF air on earth Is highly
| annoying and injurious. Air far below
| saturation point has an injurious effect
upon the skin, which it dries, roughens
| and cracks. while during the winter the
body heat is too rapidly distracted. caus-
| Ing sensation OF chilliness, II no more
severe symptoms Of cold. Air nearly or
quite saturated is equally unpleasant dur
| ing the summer season. The perspiration
| instead or being conveyed away in the
form OF vapor from the body as rapidly as
IT Is Secreted. stands in beads upon the
| skin. and the body heat deprived Of its
chie1 outlet and source Of ioss-the latent
heat OF evaporation accumulates and
causes discomfort
Besides these, dust-laden air or a mud
covered earth may be mentioned as real
ihconSeniences. But of more vital concern
Is the untaNorabIe effect upon plant devel-
opment which water-Satu turated soil has
A proper balancing of rainfall and eyap-
ofaton is essential TO our comfortable ex-
lstence upon earth. When active condeu-
sation has set in, the water vapor furnish
es welcome shade from over-fierce solar
rays, and always water vapor in the air
checks the loss OF heat from the earth's
eAAAoSe. III HlSlier realms or our
sHe nature the phenomena connected with
evaporation and condensation of water
rouses the reasoning and the imagining ca
pabilties OF our being. We naturally in
qulre what Is evaporation? What are the
forces producing this changer What are
It's effects? The unromantic dweller on
loWland plains may see on his horizon
splendid mountain SUBMITS and Cordille-
ran ranges represented in cloudland by bi-
io"y masses or minute water drops.
Phenomena of Evaporation.
The nature of the phenomena occurring
during evaporation. concerning as they do
the ultimate molecules of which the SUBJ
stance is composed. can not be easily un-
derstood. One theory is that the molecules
OF liquid move on the average mora
slowly than those Of its corresponding
Vapor, put that some molecules move more
rapidly than Others and these rapidly NOV
ing particles are constantly escaping from
the liquid to lead for a time a free exist
ence In the gaseous state. There are OBJ
oections to this theory, one being that most
nulds VIII entirely evaporate, and it does
not appear how under certain circum-
stances the speed of the motion of their
particles is increased. Neither does the
theory explain why evaporation Is more
| RAPID under decreased pressure. Late ex-
periments seem to point to the conclusion
that all bodies are giving of streams Of
particles much smaller than atoms would
appear to be. II this be the case when
| Inc under what conditions and impelled by
what forces they again unite and reform a
| liquid. Heat undoubtedly has something to
do with the process, but other molecular
FORCES are probably acting in conjunction
| to produce the phenomena of evaporation.
In the case of our three upper lakes
| Superior, Huron and Michigan-the water
surface is 81 900 square miles the area Of
land draining into them 10000 SQUARE
| miles. In the Caspian basin the ratio OF
water TO land Is l to 4, and the balance OF
rainfall and evaporation is being maintain
ed without any DISCHARGE Would it not
also be maintained in the great lakes basin
with one square mile of water to two
square miles of land area draining into II
under like conditions? 1t would appear al
most certain that vast subterranean riy-
ers must find their way into the lakes from
outside their basin. In most places
throughout the Mississippi valley under
| exist and have been struck in sinking
wells. In Montana wells often flow with
| high pressures.
Temperature Of Lake Water.
The temperature Of the water In the
lake Is too low and its color too clear to
suggest that much Of it had it's origin in
| northern peat bogs. The Mediterranean
waters vary in temperature from 30 de-
grees Fahrenheit on the surface to 55 de-
grees Fahrenheit In the deeper portions
during the hottest parts OF the year The
Mediterranean in deepest parts is four
times as deep as our upper lakes. The
water in our lakes Is much colder in pro-
portion to that of the Mediterranean Lake
Superior water is icy cold at all times and
Lakes Michigan and Huron but few
degrees warmer. The temperature suggests
supplies drawn from far-of sources and
conveyed in Subterranean channels.
The Missouri river loses one-half itS
water while passing around the Great
Bend, in North Dakota. Other large
streams in the western country lose much
of their volume in passing over the porous
cretaceous strata, and this probably gives
rise to the vast sytsem Of underground
waters, tapped in SO many places in the
central parts of the continent