L. Loomis— United States Weather Maps. 15 
the 22d and 23d; snow and rain fell at Virginia City; and it 
was cloudy at Corinne, Fort Sully, ete. The second oval on 
Plate 11 shows the isobar 29°7 at 74 a. M., Sept 23d. On this 
day rain or snow fell at Fort Benton, Virginia City, Cheyenne, 
Fort Sully, Breckenridge, and several places further east. The 
third oval shows the isobar of 29-7 at 74 A. M., Sept. 24th. The 
longer axis of this oval, instead of being turned east and west 
as on the two preceding days, was now turned nearly northeast 
toward Lake Superior. Near the center of this oval the bar- 
ometer stood at 29.36. On this day over half an inch of rain 
fell at St. Louis, Cairo, Davenport and Duluth, and a less 
amount at other places. 
the morning of Sept. 25th, the center of the isobar 29-7 
was nearly over the middle of Lake Superior. On the north, 
this isobar extended beyond the range of our observations, so 
that only the southern portion of the curve could be definitely 
located. At Duluth the barometer stood at 29°33. On this 
day considerable rain fell at Duluth, Escanaba, Oswego, Kings- 
ton, ete. During the next 24 hours the center of this storm 
remained nearly stationary over Lake Superior, but on the fol- 
lowing day it advanced northeastward, and passed beyond the 
range of our observations. In three days the center of the storm 
traveled eastward about 1280 miles, being at an average rate of 
18 miles per hour. 
It seems probable that this storm originated, or at least was 
first developed into a storm of considerable magnitude, through 
the collision of moist air from the Pacific Ocean with some of the 
high mountain peaks in Oregon, resulting in a heavy fall of rain 
orsnow. The fact which is of special interest is that this storm - 
when once organized, traveled over all the mountain ranges 
tween the Pacific Ocean and Lake Superior without sensible 
obstruction. The same fact is noticeable in the storm of Sept. 
19-22d, and several other storms of the same month. We hence 
infer that those storms which come to us from Nebraska some- 
times originate in the mountains of Oregon, and probably some- 
times come from the Pacific Ocean, whence they travel east- 
ward, occasionally passing entirely across the continent to the 
Atlantic Ocean. 
The reductions described in the preceding article have all 
i i bor has been 
r 
paorned by Mr. Edward 8. Cowles, a graduate of Yale Col- 
ege of the class of 1873. 
