Observations of the United States Signal Service. 17 
Number of stations within the area of low barometer. 
| 
| No. ae 
No. |Stations No. |Stations|| No. |Stations|| No. |Stations|| No. |Stations 
"51! 70 || 60 | 47 || 35| 43 || 74| 39 || 161 32 || 59| 30 
101 | 67 || 39 | 45 7 | 43 |hoo| 39 || 24] 31 || 61 | 30 
mu | 58 || 70| 45 liv! 42 || 58} 35 || 36] 31 || 90] 30 
20 | 48 52 43 71 39 || 6 33 29 |. 30 
travel to the eastward. In several cases the center of least 
pressure was beyond the limits of the United States so that it 
is impossible to assign satisfactorily either the direction of their 
progress or their rate of motion. The table on pages 14 and 
15 shows the best results I have been able to deduce from the 
isobar 29-8 for October 19th; the next curve represents the 
isobar 29°6 for October 20th; and the most eastern curve 
represents the isobar of 29°8 for October 21st; each of the 
curves corresponds to the 4.35 P. M. observation. It will be 
seen that during the first twenty-four hours, the center of least 
pressure moved only about five miles per hour; but during 
the next twenty-four hours the average motion was twenty-two 
miles per hour. During these forty-eight hours not a drop of 
rain was recorded at any station within the area of a pressure 
less than thirty inches, although on the 20th of October this 
area had a diameter of 1,500 miles. 
The observations on the amount of cloudiness at the different 
stations confirm the observations of rain-fall. The following 
table presents a summary of these observations. Column 2 
shows the number of stations within the area of low barometer 
(i.e, less than thirty inches pressure) at which the sky was 
reported to be entirely clear at the dates given in column Ist, 
xcept that the air was very generally reported to be smoky or 
azy; column 8d shows the number of stations at which the 
7 rtly cloudy; and column 4th shows the number 
Stations at which the sky was entirely overcast. 
The following are the stations at which the sky was reported 
to be overcast, viz: October 19.2, Virginia City and Duluth; 
20.2, Corinne, Cheyenne and Duluth; 20.8, Denver, Cheyenne 
Am. Jour. grees Series, Vou. XIV, No. 79.—Juxy, 1877. 
