Practical Exercises in Elementary MeteorologyWard, Robert DeCourcy
Science
Practical Exercises in Elementary Meteorology
Ward, Robert DeCourcy
Meteorology
The Washington weather map is about 24 by 16 inches in size, and is newly
lithographed each day. The total number of maps issued from the central
office during the fiscal year ending June 30, 1898, was 310,250. In
addition to these, there are now 84 stations of the Weather Bureau in
different parts of the country, at which daily weather maps are issued and
local forecasts made. These latter forecasts are made by a corps of local
forecast officials, each of whom has to make the weather prediction for
his own district. At first, and until within a few years, one predicting
officer in Washington made all the forecasts for the country, but it was
found better to have the country divided into geographical sections, over
each one of which the meteorological conditions are fairly similar, and to
have a local forecast official in charge of each section. These local
forecast officials have the double advantage of being able to study the
weather conditions over the whole country, as sent them by telegraph each
morning, and also of knowing the special peculiarities of their own
regions. This enables them to make more accurate predictions than can be
made by an official who may be one or two thousand miles distant, in
Washington.
The greater portion of the maps issued at the map stations outside of
Washington are prepared by what is known as the chalk-plate process,
suggested by Mr. J. W. Smith, local forecast official at Boston. This
process is as follows: A thin covering of specially prepared chalk, 1/8 of
an inch in thickness, is spread upon a steel plate of the size of the
prospective weather map. On this chalk are engraved, by means of suitable
instruments, the various weather symbols, the lines of equal pressure and
of equal temperature, and the wind arrows. The plate is then stereotyped
in the ordinary way, and printed on a sheet prepared for the purpose,
which has a blank outline map of the United States at the top, and space
in the lower half for the forecasts, summary, and tables.
The size of the chalk-plate map itself is 10 by 6-1/2 inches; the size of
the whole sheet, which includes also the text and tables, 16 by 11 inches.
Weather maps prepared by the chalk-plate process are now issued from 28 of
the 84 stations which publish daily maps. At the remaining stations the
maps are prepared by a stencil process, the size of the map being 13-1/2
by 22 inches. The total number of weather maps issued at the various
stations during the fiscal year 1897-1898 was 5,239,300.
Public-domain text, read in full here on John Shaqi.
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