The Vermont watchman. [volume] (Montpelier, Vt.) 1883-1911, 1891-09-30
Weather.
LECTURE BY PROFESSOR DoLBEAR OF
TUFTS COLLEGE.

Friday evening, 18th inst, in the chapel Of
the Vermont Methodist Seminary, Professor
Dolbear of Tufts College lectured in an in
teresting and instructive manner on
" weather" The speaker declared that no
later than twenty years ago there was no
science OF weather, because there was no
data To-day the United States has posted
observers in all parts of her territories who
twice in twenty-four hours telegraph
their observations to a central bureau at
Washington, where in turn they are care
fully plotted, traced and studied and be-
come the basis of the estimated weather
bulletins OF each day. The ultimate prin-
ciple underlying air and water movements
is convection. This term describes the pro-
cess through which universal currents are
produced in fluids through expansion due
to heat. The hard beatings of the sun upon
equatorial earth raises the temperature of
the surrounding air This produces expan-
sion upwards, creates a growing vacuum
which under-currents of cold air from the
North seek to neutralize. Thus come to
pass two currents of air, one flowing north
ward from the equator, one southwark from
the pole. Their line of motion would be
directly north and south, if it were not
modified by the shape of the continents
mountain heights, and the revolution of the
earth upon its axis. At the equator the
earth's surface, and hence its supernambent
atmosphere, has a rotary velocity, due east
the pole there is no surface motion. Hence
between these points there must occur not
only constant diminuton in the great ini-
tial velocity of the current but through the
composition of forces, DETECTION to the
north and east when starting from re
equator, and to the southwest when starting
from the pole.
AT some point between these oppos-
ing currents come in conflict and there
results motion Of rotation in large bodies
d.fs anhs -.
Der, IS dtUdyS from UeSt to east. This mo-
ton is the storm. Its approach is foretold
by the falling barometer and the direction
Of the wind. 1t brings the rain. A special
function of the air is that of absorbing
moisture. Suppose" said Professor Dol
bear, {" that we consider a single acre of
land and one inch of rain fall that would be
AZ, $50 square feet one inch under water or
6,212,64O cubic inches of water, about 10000
liquid gallons or 100 tons of water to the
acre" This process Of absorption is termed
evaporation. Distribution is due to con.
YeCtlon and rainfall to condensation. 1t
is a round and round process, nature work
ing in perfect circles for the universal
blessing. Remembering the foregoing
principles and considering that condensa-
ton is induced by lowering temperatures it
becomes possible to draw several interest,"
ing and useful deductions for this section.
IA storm is large body of air rotating
from east to west.
IF you stand directly with your back
towards the winds approach, the storm
center is on our left hand.
3-If the storm center be at Washington
the wind will be from the southeast at New
York city.
NEARLY all of the rain fall must be on
the south and southeast sides of the storm
IA wind from the south or southwest
portends rain. Its cessation will be fore
told by change in the winds quarter.
Many of our storms originate in Manitoba
and upper regions where there is no service
and therefore their approach are frequently
unherdlded in time. This branch of the work
can be rendered effectual only by Canadian
cooperation and that, at present, is out of
the question. 1t cannot be told either at
any rate not far in advance, whether
storm, known to be on its way from the
northwest, will swing down and then up
TO the st. Lawrence valley or whether it
will down itself off the New Jersey coast
or designate its force on the mountain
lands between. On the contrary the storms,
that start from the West Indies and blow
with fearful violence along the Atlantic
coast lie in the knowledge of the weather
bureau, and much valuable work is regu-
larry being done in protecting shipping
from their ravages by timely warning.
These latter storms, however, develop
popularity not yet explained, that of
standing still " when they reach New
England, and lasting for several days, or as
tne lecturer nau III, - OF uuWlnulnR them
selves " off our coast. 1t was this feature
of these storms which the great blizzard, in
which Roscoe Conkling lost his life not
long ago, demonstrated
The tornado is an off-shoot of larger
storms and regularly occurs in the south
east quadrant of the rotating air mass. 1t
always acts from northwest to southeast,
over band of limited area and is most dis
tinctive at a distance of from 400 to 800
miles from the storm center. Asvery many
may accompany single storm, prediction
regarding them is highly uncertain. Es-
cape from tornadoes lies along a line at
right angles to their line of approach
In closing, Professor Dolbear spoke with
regret of any existing objections to the
weather bureau. Its work he declared
was neither guess nor a prophesy but a
scientific estimate based upon carefully OBJ
served data in great numbers. If its esti-
mate proved to be correct four times in
five, it has demonstrated its utility and its
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