| 2is re represented on Plate I accompanying my fifth paper 
EF. Loomis—Ohservations of the U. S. Signal Service. 3 
and Pac. O. denotes Pacific Ocean; column 10th shows the 
highest pressure observed at any station at the date mentioned 
in column 2d; and column 11th indicates the station at which 
this pressure was observed. Each of these areas of low pressure 
appears to have moved eastward, and can be traced to the 
Atlantic coast. Column 12th shows the date at which the cen- 
ter of low pressure reached the Atlantic coast, _ column 13th 
shows Has latitude of the low center at that ti 
A comparison of these cases shows that pace all occurred 
dion the six colder months of the year, and they were most 
numerous in January. In a majority of the cases the wind 
blew from the south, and in only three cases did the wind blow 
In doy -SiX per cent of the cases, the pressure at Portland. 
was lower than at any other station at the same hour; in twenty- 
seven per cent of the cases, the lowest pressure was ‘at Virginia 
City or Fort Benton ; in thirteen per cent of the cases, the lowest 
aegis was at Fort Sully; and in the remaining cases the 
owest pressure was at some station still further east. com- 
parison of the observations at Virginia City with those at 
m8, phi stations indicates that the readings of the barometer 
at Virginia Cit a Mee and accordingly they have all — 
been Bopha by 0 
With but sind encpin all of these cases of low pressure 
eee to have originated north of Portland, and generally west 
that station. In the table, this region is designated by the 
term British Columbia. It is probable that in some of these 
cases, and perhaps in all of them, the area of low pressure was 
first formed over the Pacific Ocean. No. 10 was apparently 
formed on the east side of the Rocky Mountains, but north of 
be fea States, a es designated as Canada N. W. Nos. 
17 were apparently formed over the Pacific Ocean, near 
bed Cae of San Francisco. 
In a majority of these cases there was an area of high barom- 
eter on the east side of Portland, at an average distance of about 
1500 miles. In one case the barometer rose to 30 95 inches ; 
In six cases the barometer rose as high as 30°75 inches; ins 
one-third of the cases the pressure rose to 30°5 inches; and in 
more than two-thirds of the cases the pressure rose to 
inches. In five cases (out of sixty-three) there was no stato: : ee 
within the limits of the United States where the pressure rose i 
as high as 30°15 inches at the dates mentioned. No. 17 i is ie : 
fel 
resented on Plate IIT accompanying the present. ape a 
