E. Loomis— Observations of the U. S. Signal Service. 95 
found, but the general features of the curves are but little 
changed. e breaking up of the area of high pressure into 
three subordinate areas is distinctly indicated, and it is scarcely 
to be expected that this feature will be made to disappear b 
a longer continuance of the observations. It appears probable 
that there is a permanent cause for this peculiarity, and it may 
perhaps be ascribed to the usual course pursued by barometric 
minima. The centers of great storms, particularly in winter, 
generally follow the eastern slope of the Rocky Mountains 
until they reach latitude 40° or a little further south, after 
which they turn eastward and soon incline somewhat to the 
north of east. This low barometer is partly compensated by 
the high pressure which succeeds it, but this compensation 1s 
apparently not quite complete. 
The following table shows the data for the month of July 
for the same stations named in the table on page 94, and the 
arrangement of the table is the same. 
July observations. 
Reduc, barom. 
Stations Alti- | Mean | Ther- 
3 tude. | barom.| mom. | Dun- Diff. 
woody. Loomis. 
° 
Santa Fé 7000 | 23°353; 69°02 | 29°863) 29°884' —-021 
Dodge City 2486 | 27-403! 77°53 *859 "869 —‘010 
Denver 5269 | 24°873) 73°16 884 902) —’018 
North Platte 2838 | 27°065' 74°77 872 879 007 
Cheyenne 6057 | 24°143; 69°60 *854| -883 —°029 
Salt Lake City | 4362 | 25°628, 76°84 “798 “816; —"018 
Yankton -979| —005 
Virginia City | 5694 | 24339 64:54| -788| -809| —-021 
Bismark 1706 | 28-143! 70°17) -880! 884 —-004 
It will be noticed that the differences between the results by 
Dunwoody’s Tables and my own are quite small, showing that 
Dun woodv’s Tables give very good results for altitudes as great 
as 7,000 feet, for summer as well as winter. . : 
Plate III shows the isobars drawn to represent the preceding 
observations as well as those at other stations of the Signal Ser- 
‘ice. ese curves bear a close resemblance to those de- 
nved from my first collection of observations. The area of 
minimum pressure extends from Salt Lake City northward, and 
the pressure increases on each side of this area, but most rap- 
idly on the west side. These curves generally represent the — 
observations very well; but there are some exceptions, particu- 
larly at the stations between the Rocky Mountains and Lake 
Michigan. The greatest discrepancy is at Yankton, where the 
observed height exceeds that shown on the chart by 0-07 inch; 
While at Chicago the observed height is less than the chart by 
