The circumstance which renders the coming total eclipse of the sun, on
May 28, 1900, of special significance to thousands of people who might
otherwise entirely overlook the occasion is the fact that the path of
the moon’s shadow over the surface of the earth, or the track of the
eclipse, is in such a convenient locality--namely, in our Southern
States--as to render the places of visibility easily accessible.
Instead of being obliged to go to the ends of the earth, at a heavy
expenditure of time and money, all the while running the risk of not
seeing the eclipsed sun on account of prevailing cloudiness, we are
fortunate this time to have the show at home in our own country.
While many foreigners will be induced to come to the United States
to make observations, it is certain that more people will be in a
position to see this eclipse with a minimum amount of trouble than has
ever happened before in the history of eclipses, at least since the
telescope was invented and careful records of the phenomenon preserved.
The track of May 28th enters the United States in southeastern
Louisiana; passes over New Orleans, La., centrally; over Mobile, Ala.,
which is on its southern edge; over Montgomery, Ala., on the northern
edge; over Columbus, Ga.; south of Atlanta, Ga., which lies about
twenty-five miles to the north of it; near Macon, Milledgeville, and
Augusta, Ga., Columbia, S. C., Charlotte, N. C.; over Raleigh, N. C.,
which is ten miles north of the central line; and over Norfolk, Va.,
fifteen miles north of the center. The track is about fifty miles
wide in all parts, and the duration of the eclipse varies from one
minute and twelve seconds near New Orleans to one minute and forty-four
seconds near Norfolk, on the central line. These durations diminish
from the maximum at the middle of the track to zero at the northern
and southern limits of it, so that an observer must be stationed as
near the central line as possible in order to see much of the eclipse.
The population of several of the above-mentioned cities is at present
as follows: New Orleans, 242,000; Mobile, 31,000; Montgomery, 22,000;
Columbus, 20,000; Atlanta, 66,000; Raleigh, 13,000; and Norfolk,
35,000. It is evident that with very little exertion more than 500,000
people can see this eclipse. It is most fortunate that the track
passes near so many cities, because, with their facilities for the
accommodation of visitors, many will be induced to undertake excursions
with the purpose of taking in this rare sight, and a little enterprise
on the part of railroads and transportation companies might easily
increase the numbers. If people will go to a parade, yacht race, or
an exposition, and consider themselves paid for their expenses, then
surely they will find in this great spectacle of Nature not only an
object of wonder and beauty, but also one of peculiar instruction in
many important branches of science. All educators who can induce their
pupils to make such an expedition will implant a love of astronomy in
many impressionable minds which will become a source of pleasure to
them for the rest of their lives.
[Illustration: CHART I.--TRACK IN THE UNITED STATES OF THE TOTAL
ECLIPSE OF MAY 28, 1900. (By permission of the United States Weather
Bureau.)]
Out of about seventy eclipses of the sun which have occurred somewhere
in the world within the nineteenth century, there have been only
eight total eclipses of more or less duration visible on the North
American continent. The others happened in places often remote from
civilization, and sometimes in entirely inaccessible localities, as
over the ocean areas. The difficulty of transporting heavy baggage
to the remote parts of Asia, Africa, or South America is such as to
preclude all but a few scientists from any effort to observe eclipses.
The writer was much impressed with the formidable nature of undertaking
to establish eclipse stations in places which are distant from centers
of population by his own experience on the West African Eclipse
Expedition, sent out by the United States Government, for the eclipse
of December 22, 1889, to Cape Ledo, on the west coast of Angola, about
seventy miles south of St. Paul de Loanda. Nearly eight months were
consumed in the course of the preparations at home and in the voyage
out and back. The expedition, it should be said, however, went to Cape
Town, South Africa, and halted also at St. Helena, Ascension Island,
and Barbados for magnetic and gravity observations, so that all this
time should not be charged to the eclipse proper. We sailed in the
old frigate Pensacola, the companion to Farragut’s flagship, the
Hartford, with Captain Yates. In earlier days Admiral Dewey commanded
this ship, and the expedition was fitted out while he was in charge of
the Bureau of Equipment at Washington. The same fine courtesy that has
become so well known to his countrymen was at that time extended to all
the members of the expedition.
The cloudiness along the track of the eclipse in the Southern States
on the 28th of May, 1900, is evidently a matter of much importance not
only for all astronomers, but for non-professional spectators. If it
could be foretold, with the same precision as the astronomical data
give the time and the place of the occurrence of the eclipse, that
the day itself will be fair or cloudy, or that certain portions of
the track will be clear while others will be obscured, it would be of
great benefit. The cost of these scientific expeditions is very great,
since it is necessary to transport many heavy and delicate pieces
of apparatus into the field, including telescopes, spectroscopes,
polariscopes, and photographic cameras, and set them up in exact
position for the day of observation. The expedition to Cape Ledo, West
Africa, in 1889, carried out a large amount of material, prepared it
for work during the totality, and then entirely lost the sun during
the critical moments by a temporary obscuring of the sky through local
cloud formations. There had been some clouds at the station during
the forenoons for several days preceding the eclipse, but the sky was
usually clear and very favorable during the middle of the afternoons.
The totality came on at three o’clock, and photographs of the sun were
taken at first contact about 1.30 P. M.; clouds thickened, however,
and totality was entirely lost, while the sun came out again for the
last contact at 4.30 P. M. This was a very trying experience, and of
course could not have been avoided by any possible precautions. Some
astronomers have thought that the advance of the moon’s shadow is
accompanied by a fall in temperature, and that cloudiness is more
likely to be produced from this cause.
Soon after the West African eclipse Professor Todd, of Amherst
College, proposed that more systematic observations be made for the
probable state of the sky along eclipse tracks, with the view of at
least selecting stations having the most favorable local conditions.
The method was tried in Chili, April, 15, 1893, and in Japan, August
8, 1896, with some success. Heretofore the available meteorological
records, which were originally taken for other general purposes,
had been consulted, and some idea formed of the prevailing tendency
to cloudy conditions. In accordance with the improved method, the
United States Weather Bureau has been conducting special observations
on the cloudiness occurring from May 15th to June 15th in each
of the three years 1897, 1898, and 1899, for the morning hours of
the eclipse--between 8 A. M. and 9 A. M. A tabular form was sent
through the local offices to such observers as were willing to act as
volunteers in making these records, and their reports have been studied
to discover how the cloudiness behaves along the eclipse track at that
season of the year. Each of the three years gives substantially the
same conclusion--namely, that there is a maximum of cloudiness near
the Atlantic coast in Virginia, extending back into North Carolina,
and also near the Gulf coast in Louisiana and in southern Mississippi,
while there is a minimum of cloudiness in eastern Alabama and central
Georgia. The following table will serve to make this plain:
_The Prevailing Cloudiness of the Sky along the Eclipse Track._
-------------------+--------------+------------------
STATE. | General sky. | Sky near the sun.
-------------------+--------------+------------------
Virginia | 40.3 | 38.0
North Carolina | 32.4 | 29.9
South Carolina | 26.4 | 24.9
Georgia | 16.4 | 14.7
Alabama | 18.2 | 17.7
Mississippi | 30.8 | 29.2
Louisiana | 32.9 | 27.7
-------------------+--------------+------------------
The significance of these figures is shown by transferring them to a
diagram, given on Chart II, which indicates the average cloudiness
prevailing over the several States where they are crossed by the track.
The marked depression in the middle portions, especially over Alabama
and Georgia, indicates that the stations in these districts make a
much better showing than those nearer the coast line. The reasons for
this difference are probably many in number, but the chief feature is
that the interior of this region, especially over the higher lands of
the southern reaches of the Appalachian Mountains, which are from six
hundred to one thousand feet above the sea level, is somewhat freer
from the moisture flowing inland from the ocean at that season of the
year. The table shows also two divisions, one for the “general sky,”
wherein the relative cloudiness was noted in every portion of the
visible sky, and for the “sky near the sun,” where the observation was
confined to the immediate vicinity of the sun. The two records agree
almost exactly, except that the sky near the sun averages a little
lower than the general sky. This indicates that although the sun will
be seen in the morning hour of May 28th, when it is only from thirty
to forty degrees above the horizon, yet this is not an unfavorable
circumstance. The low altitude, on the other hand, makes it easier for
those at the instruments to enjoy a more comfortable observing position
than if it were nearer the zenith, where one must look directly upward.
Of course, a storm of some kind may occur on that day to modify these
general weather conditions and upset all calculations. While the cloud
observations suggest that Georgia and Alabama have the best sites for
the eclipse, it must be remembered that the duration is about one
minute and twenty seconds in Alabama, and one minute and forty seconds
in North Carolina. As a gain of twenty seconds in observing time will
be considered by many of sufficient importance to take chances on
the cloudiness, stations will be selected in North Carolina for that
reason, although the probability for minimum cloudiness is twice as
good in Georgia and Alabama. The table shows that the chances are only
one to six against observers located in these States, while near the
coast they are about two to six against them. On the whole, the general
result is that observing in this region ought to be successful, because
the favorable chances for good weather are above the average at that
season of the year.
[Illustration: CHART II.--PROBABLE STATE OF THE SKY ALONG THE ECLIPSE
TRACK.