12 E. Loomis— United States Weather Maps. 
ally cases in which the center of the storm was near the north- 
ern boundary of the United States, and the isobaric curve was 
incomplete on the northern side for want of observations. In 
nearly half the cases, the isobaric curve selected for measurement 
was the lowest isobar shown on the maps; but whenever there 
was a larger curve traced for at least one-half of its circuit, the 
latter curve was taken in preference. A line was then drawn to 
represent the longer axis of this curve, and the length of this 
line was measured; or when the curve was incomplete the 
length of half of this line was measured. The length of the 
line drawn through the center of the isobaric oval at right 
angles to its longer axis was also measured, and the direction 
of the longer axis was determined by a protractor. The result 
of these comparisons was as follows: 
In 55 per cent of the whole number of cases, the major axis 
of the isobar exceeded the minor axis by one-half of its whole 
length. In 30 per cent of the cases, the major axis was more 
than double the minor axis; in nine per cent of the cases, the 
major axis was more than three times the minor axis: and in 
four per cent of the cases, the major axis was at least four times 
the minor axis. 
These results appear to me to prove that the centrifugal 
force arising from the circulation of the wind around the storm 
center cannot be the principal cause of the fall of the barome- 
ter, for otherwise the shape of the storm would be more nearly 
circular. 
With regard to the direction of the major axis of the isobars 
there is no uniformity. e major axis may have any position 
whatever; but the direction which is decidedly more frequent 
than any other is about N. 40° E. It will be readily perceived 
that this direction is almost identical with the general course 
of the Atlantic Coast, and also with the range of the Alleghany 
Mountains; and it might be supposed that one or both of these 
circumstances had some influence in determining the position 
of the isobaric curves. In order to decide this question, I 
divided the observations into two classes by a line drawn from 
Buffalo to Mobile; one class representing the storms of the 
Mississippi Valley, and the other representing the storms of the 
Atlantic Coast, and found the results in the two cases nearly 
identical. The easterly inclination of the storm axes is quite 
as decided in the Mississippi Valley as upon the Atlantic Coast. 
It may, therefore, be reasonably inferred that not only the 
elongated form of storms, but also the prevailing direction of 
their longer axes, is mainly dependent upon general, and not 
upo uses. 
sy as 
