12 E. Loomis—Observations of the U. S. Signal Service. 
mometer fell as low as — 30°, and five of these cases occurred 
Breckenridge. In more than half of the whole number of 
cases the thermometer fel] as low as zero of Fahrenheit. The 
highest temperature reported in any one of these cases was 48° 
at Cape Rosier, September 18.2, 1874. This is a station where 
the daily range of temperature is unusually small, being influ- 
enced by the temperature of the Gulf of St. Lawrence. In all 
of these cases the average temperature at Breckenridge and its 
vicinity was very much lower than at any of the stations east 
of longitude 86°. 
contributes to increase its pressure. This point will be further 
considered on page 
With a single exception, these areas of high barometer ap- 
peared to come from British America. About half of them 
appeared to originate on the west side of the chain of the 
Rocky Mountains and half on the east side; but on account of 
the small number of stations of observation it is impossible to 
trace these areas of high pressure satisfactorily to their origin. 
Each area of high pressure appears to have commenced with a 
moderate elevation above 30-00 inches ; this elevation gradually 
increased as the wave advanced, and generally attained its 
maximum over Dakota or Minnesota. In one case (Jan., 1873,) 
pressure seems to have been first developed in the neighborhood 
of Arkansas, and increased slowly in magnitude as it drifted 
eastward, attaining a baighs of 30°66 inches at Charleston, Jan- 
uary 12th, 1873. 
In nearly all of these cases an area of low pressure immedi- 
ately preceded the area of high pressure. When the center of 
igh pressure is west of the Mississippi, an area of low pressure 
is almost invariably indicated by the observations near the 
Atlantic coast. When the center of high pressure is near the 
Atlantic coast, there are no stations of observation where this 
30. The vare case in <hidh an area of hip pressure "was not 
immediately preceded by an area of low pressure on the east 
o. 9. This case, which has already been referred to, 
apparently resulted from an area of low pressure prevailing in 
the northern part of the United States. We thus find that 
areas of very high pressure are almost invariably preceded by 
an area of low pressure on the east side, generally at a distance 
2 o of about 1,200 miles. 
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