20 E. Loomis—Observations of the U. S. Signal Service. 
~T 
several days distinct from each other. Such were Nos. 8, 4 
and 15. In N e storm was apparently diverted North- 
ward by the low area on the north-northeast. In No. 16 the 
on the southeast and another on the southwest, and the low 
area pushed in between them. In the United States it is fre- 
quently observed that when two areas of high pressure approach 
within a few hundred miles of each other, a low center is devel- 
oped between them. A similar case occurred in No. 6 between 
Sept. 11th and 12th. In No. 20 the observations do not indi- 
cate any decided low center on the north or west, yet the 
pressure was every where either below or but little above the 
normal over the North Atlantic Ocean and North America. 
hus we see that in Europe and over the Atlantic Ocean as 
well as in the United States, the influence of one area of low 
pressure upon another is a very common cause of abnormal 
movements of storm centers. 
In preparing the materials for this article I have been as- 
sisted by Mr. Henry A. Hazen, a graduate of Dartmouth Col- 
lege of the class of 1871. 
Norg.—Since the preceding was in type, I have received 
Hoffmeyer’s charts for November, 1876, from which it oid porte 
that on the 12th of November, 1876, there was an area of low 
pressure (730 to 725) west of Ireland; and the apparent west- 
wa ovement of No. 9 on page 18 was plainly due to the 
influence of this low center. I have also received the Inter- 
national Bulletin for October, 1880, from which it appears that 
on February 16th there was a low center (28°40) west of Ire- 
land, and the apparent westward movement of No. 21 on page 
18 was plainly due to the influence of this low center. 
. 
