Marcu 1, 1901.] 
the anti-cyclone is a secondary phenomenon— 
a part of the cyclone. The eclipse cyclone, to 
keep pace with the eclipse shadow, must con- 
tinuously have formed within the shadow, and 
must have dissipated in the rear almost in- 
stantly. The motion may thus be considered 
to have a certain analogy to wave mo ion. 
In the light of his discovery that the brief 
fall of temperature in the eclipse can produce 
a well developed cyclone, which accompanies 
the eclipse shadow at the rate of about 2,000 
miles an hour, Clayton believes that the fall of 
temperature due to the occurrence of night 
must also produce, or tend to produce, a cold- 
air cyclone. Since the heat of day produces, or 
tends to produce, a warm-air cyclone, there 
must tend to occur, each day, two minima of 
pressure, one near the coldest part of the day 
and another near the warmest part of the day, 
with areas of high pressure between them due 
to the overlapping of the pericyclones surround- 
ing the cold-air and the warm-air cyclones, 
respectively. These causes must, in the opin- 
ion of the author, produce entirely, or in part, 
the well-known double diurnal period in air 
pressure, a question which has long puzzled 
meteorologists and for which as yet no wholly 
satisfactory explanation has been offered. The 
surface winds at Cordoba (Argentina) and at 
Blue Hill are in general found to be in opposite 
directions, and to indicate a circulation of the 
wind around two cyclonic centers passing along 
the equator, and an outflow from high pres- 
sures half way between them. 
Clayton’s conclusions, which are to be pre- 
sented in greater detail in a forthcoming Bul- 
letin of the Blue Hill Observatory, are of the 
greatest interest and importance. His expla- 
nation of the diurnal variation of the barometer 
seems to have in it many evidences of being 
the best yet offered to account for this puzzling 
phenomenon. Meteorologists will now look for- 
ward to future solar eclipses with greatly in- 
creased interest because of the importance 
which Mr. Clayton has shown to be attached 
to eclipse meteorology. It is to be hoped that 
Mr. Clayton may have the time and the oppor- 
tunity to extend his investigation further in 
connection with previous eclipses. 
R. DEC. WARD. 
SCIENCE. 
393 
THE MAGNETIC SURVEY OF THE UNITED 
STATES. 
On July 1, 1899, a special division of the 
Coast and Geodetic Survey Office was created 
by the Superintendent to take charge of the 
magnetic survey of the United States and the 
countries under its jurisdiction, which up to 
that time had been conducted under the super- 
vision of the Computing Division of the Coast 
and Geodetic Survey. Since that date magnetic 
observations, namely, declination, dip and in- 
tensity of magnetic force, have been made up 
to December 31, 1900, at about 500 stations dis- 
tributed over the United States, Alaska and the 
Hawaiian Islands. At most of the stations per- 
manent marks have been established for the use 
of the surveyor. Special consideration has also 
been given to the needs of the mariner, espe- 
cially in Alaskan waters, where occur places of 
pronounced local attraction, affecting the com- 
passes on board ship all the way from one-fourth 
of a point to four points. 
Special stations known as ‘ repeat,’ or ‘secu- 
lar variation’ stations, have also been estab- 
lished in different parts of the country. At 
these, observations will be repeated at stated 
intervals in order to determine the amount of 
secular change in the magnetic elements. It is 
the endeavor whenever possible to establish 
such stations in the vicinities of colleges and 
universities, as experience has shown that on 
college grounds we may hope for a permanency 
of station for a fairly long interval. 
Of special state surveys mention may be made 
first of the completion of the magnetic survey of | 
Maryland, which was undertaken primarily by 
the Maryland Geological Survey, with assistance 
rendered by this Bureau ; second, the comple- 
tion of the magnetic survey of North Carolina, 
conducted under the joint auspices of this 
Bureau and the North Carolina Geological Sur- 
vey ; third, the completion of the magnetic sur- 
vey of West Virginia, and fourth, the completion 
of the magnetic survey of Iowa. 
Fair progress has also been made in the 
establishment of the Magnetic Base Stations, 
where the countless variations of the earth’s 
magnetism will be recorded photographically. 
Thus a temporary magnetic observatory has 
been in operation at Baldwin, Kansas, since 
