De RS Penge age ae ee eee a ea 
E. Loomis— Observations of the U. S. Signal Service. 18 | 
center, and the low center traveled southward apparently unin- 
fluenced by this rain-fall. There was asmaller rain area whic 
was nearly concentric with the area of low pressure, and there 
was a very slight fall of rain on the south side of the low center. 
I have madea similar comparison for each of the dates of obser- 
vation, and find the following results: In seven of these cases 
the principal rain center was about 350 miles north of the 
center of the low pressure; in four of the cases it was on the 
northeast side, and at a distance of about 500 miles; in eight 
of the cases it was on the east side, distant about 600 miles; in 
one case it was on the northwest side; in one case it was on the 
southeast side; and in only three cases was the center of the 
rain-area nearly south of the center of low pressure, viz: Nos. 5, 
28 and 29. In the last case the storm, instead of following the 
rain towards the south, immediately changed its course and 
moved off towards the east. Thus, out of thirty-nine cases we 
find only one case in which the storm seemed to follow the rain- 
area, but in half of the cases the storm traveled almost directly 
away from the rain-area, and in nearly all of the remaining 
cases the course of the storm was nearly at right angles to the 
direction of the rain-area. These facts seem to show that in 
these cases the rain-fall exerted no appreciable influence upon 
the course of the storm, and therefore no appreciable influence 
upon the fall of the barometer. This conclusion is confirmed 
by the observation of the clouds. In all the cases given in 
table IH, the average cloudiness on the south side of the low 
area was less than one-half; and in several cases the sky was 
entirely cloudless at every station on the south side of the low 
area. This was true for Nos. 15, 16, 17, 23, 24, 30,31 and 32. 
This evidence appears to me to show that heavy and exten- 
sive precipitation does not invariably precede the first for- 
mation of depression areas and’ accompany their expansion, 
as has claimed. These depression areas increased 
in intensity when the rain-fall was nearly zero, and while 
the sky on the south side was not generally overcast with 
clouds, but in several cases was almost entirely clear. In 
