E. Loomis—Contributions to Meteorology. 261 
27, 1881 to Feb. 25, 1882, a period of 91 days, during which 
time the barometer at some one of the stations was observed as 
high as 80°5 inches. On six days the barometer rose above 
31-0 inches and it attained a maximum of 31:2 inches. 
In reviewing the history of these seven years we must con- 
clude that the areas of high pressure which are so prevalent 
over Kuropasia during the winter months show no decided pro- 
gressive movement in any fixed direction. They often remain 
nearly stationary for weeks in succession, with only such ap- 
parent motion as is due to a slight decline in some places and 
a slight reénforcement in other places, resulting perhaps from 
local causes, or from some change in the circulation of the 
upper strata of the atmosphere. 
We also see that a pressure of at least 30°5 inches is almost 
uninterrupted over some portion of Huropasia during the winter 
months, and the interruptions which occasionally occur are due 
to areas of low pressure which push southward from the higher 
latitudes. The rarity of this phenomenon, and the smallness 
of the depression when it does occur, illustrate the difficulty 
which an area of low pressure experiences in penetrating a 
huge mass of very cold air. 
The accompanying plate, derived from the International 
observations, will give a more distinct idea of the relation of 
areas of high and low pressure, and will show the magnitude 
which these areas sometimes attain. ‘The plate gives the isobars 
for Dee. 15, 1882, and shows a high area covering nearly the 
whole of Europe and Asia and extending somewhat over the 
Pacific Ocean. Another high area covers nearly the whole of 
North America; an area of low pressure, with its isobars very 
much elongated, stretches entirely across the Atlantic Ocean, 
overlapping portions of Hurope and America; and another area 
of low pressure covers a large part of the North Pacific Ocean. 
Two high areas, combined with two low areas, make the entire 
circuit of the northern hemisphere near the parallel of 50°. A 
third high area, of moderate elevation, is found over the south- 
ern part of the North Atlantic, and there is a fourth high area 
of small extent over the Pacific Ocean near the coast of Cali- 
fornia. This map represents in an exaggerated form the aver- 
age distribution of pressure during the winter months, viz: 
high pressure over the continents and low pressure over the 
oceans. 
It is very rare that so small a number of areas of high and 
low pressure complete the circuit of the northern hemisphere. 
Generally the areas are much more numerous and of smaller 
dimensions; the areas are of very unequal size and are com- 
bined in very irregular positions; but during the colder months 
of the year, low areas are most prevalent over the Atlantic and 
