Evening star. [volume] (Washington, D.C.) 1854-1972, 1895-08-10

AUGUST L, 1895, AM.
each of the twenty-five cities are written
two figures, the upper giving the tempera-
ture ard the lower the pressure of the mir
at o'clock in the morning of August 1.
Thus the temperature at Boston is ii de-
grees, and the pressure 1882 inches: at
New York, 60 degrees and $3.50 inches. AS
we go towards the west the time of the
observation is earlier in the morning; thai
is. in the Mississippi valley the observer
reads his instrument at Z o'clock, local
time; on the Rocky mountain slope, at 6
o'clo ok, and on the Pacific coast, at 5
o'clock, SO that all the observers may read
at the same moment Cooperation Is.
therefore, The peculiar feature of the opera
tiers of the service. On looking over the
map the simplest question to ask is where
do the same temperatures prevail and
where are The pressureS just alike. 1t is
evidently helpful to the eye to draw line
through the places where the same condi-
tons exist, ard it is most convenient to
select the even 10 degree differences, and
the even teath-inches differences for such
connecting lines. That Is, dotted lines are
crawn through all places having the tenn
reratures 60 degrees, 20 degrees. so degre es.
and solid lines through the places having
the pressures $3.50 inches 900 inches, 30. 10
inches, barometr.c pressure. Now, in order
tc do this, it becomes necessary to inter-
potato the spaces. 1t is seen that the tenn
80 degrees, and a line can be drawn
through these, but for Jacksonville the
temperature IS only IS degrees and the So
degree Inc must run a little south of it to
! allow for the drop from 50 degrees to IS
degrees in going northward. For the 10
degree line we proceed as follows: At Ell
Paso the temperature is 6S degrees, and
| evidently the tO-degree line must lie be-
tween Ell Paso ard the SO-degree line at
| intervals CT degrees on the Ell Paso side
ara 70 degrees on the Galveston side; near
Little Rock. degrees on one side and 10
| degrees on the south side: near Lynchburg,
degrees on the north side and 10 degrees
| on the south side. The intervals to TO-
| to 10, 6 to TO- are the interpretations re-
| ferred to, and by little practice can be
very rapidly performed. In the case of the
| G0-GeSree line We have the same process
| and 1t runs through Los Angeles between
Portland and Helena, to =; between Bis
| marck and st. Paul, S to 2; between St
| Paul and Chicago, to &; north of Wash
| ihston, through New York, and west of
Boston. These dotted lines of equal tenn
perature are called isotherms.
Instructions About IsObnrs.
| In a similar manner we interpolate for
the pressure lines. Thus the 3O1o-inch
line runs between Ell Paso, s to 6, through
Dodge City. west of Omaha, between Bis
marck and st. Paul, IS to 6. returns south
| ward between Chicago and Washington, 4
to ., between st. Louis and Lynchburg. 10
| a,
to Il, and between New Orleans and Jack
sonville = to g. For the so .OO-inch line We
start between Los Angeles and Ell Paso 4
| to 2, and pass between Salt Lake City and
Denver, to L, just east of Bismarck fol-
| low the general curve Of the 80. 1O-inch line
| and pass between Washington and New
York, to 10, Another ao0O-inch line
passes through San Francisco, between
Helena and Bismarck, 4 to s. Another
30 1O-inch line passes between Portland and
Helena, to 1. A 29.90-i, CHI line passes
through New York city and a 29.So-inch
| line just north of Boston. These lines
should always be drawn SO as to harmonic
with each other, making system of curves
| that grade into each other by easy
cha 1ges. Such lines of equal pressure are
! called isot srs.
These details here given in the hope
that some will take the trouble to con-
struct little map for themselves by way
| of practice. Take some semi-transparent
| paper and trace the base lines of this map,
| the boundaries and the rivers, and locate
on it the twenty-five cities here given.
| Copy against each city the figures for the
| temperature ana the pressure, and then
| interpolste the dotted lines for temperature
ard the solid lines for pressure The fig
ures in this map are copies from the synop-
sis on the first and third columns. as print
| ed on the right-hand side OF each large
weather map issued by the weather bu-
reau. If any ore will copy the base map
and these figures for a few Gays in success
sion, and then plot in the isotherms and
| the iSobarS, and will thus watch the varia-
| BILE positions on the maps from day to day
of the lines of the same rame, a clear idea
| of the Fundamental features of the wealth
er map will soon be secured.
Symbols and Their Meaning.
In addition to these lines, the symbols
| for wind and weather are used. For wind
an arrow on the station circle pointing the
way the wind blows. and for weather.
| clear a fire line circle; cloudy, heavy
line circle; partly cloudy, bar circle; rain,
a solid circle; snow. three-bar circle. A
general rain area is shaded on the map.
Near the center CT an area Of high pres
sure above 5000 inches is placed the word
high, and near the center of region of
pressure less than 5000 inches is placed
the word low. A low pressure system is
called a storm cyclone, and the winds
| blow around the center in the opposite di-
rection to the hands of a watch. as one
looks on the watch lying upon the map
with the face up. The high pressure sys-
| tenn is called an anti-cyclone, and the winds
blow around it's center in the general di-
rection of the hands of watch, though
| in less distinct manner than in the cy-
clone. The winds always blow down the
| gradient from the high to the low, from
| the anti-cyclone to the cyclone.
| These are the chief features on any
| weather map, so far as its construction
| goes. IhOSe VINO WISH 10 learn 10 UNDER
stand the meaning of the same in regard
to the resulting weather conditions should
construct them for themselves, till familiar
with the details. Then they should care
fully compare the maps from day to day
and observe the differences that have taken
place in tweEty-four hours, in forty-eight
hours and in seventy-two hours. The east
est way to do this is to cut out the press
| map every day and lay the successive maps
| in a column, over each other, SO that the
| eye may take in at a glance the changes
| that have been going on. A short practice
| in this manner will enable one to follow
the storms as they PASS from west to east.
| and will also soon give the ability to judge
from the maps what the weather conditions
are likely to be during the following TWEEN
| :y-fUur hours.
In the next article the tracks of the
storms characteristic of August and the
| average, as well as the abnormal, weather
conditions noted in the past twenty years
will be briefly summarized.
Marriage Licenses.
marriage license has been issued to
| Arthur W. GaWen of WeStmoreland county,