12 E. Loomis—Reduction of Barometric Observations. 
There can be no doubt that the upper clouds here reported 
had a considerable elevation, which was probably at least equal 
to that of Mt. Washington, and they indicate a cyclonic motion 
of the winds about a center but a few miles E. of Mt. Washing- 
ton. I think then we may safely conclude that in a majority 
of the cases enumerated in table V, the fall of the barometer 
on Mt. Washington was due to a cyclonic movement of the 
winds which prevailed at that elevation. In the remaining 
cases the observations seem to leave it doubtful whether th 
fall of the barometer on Mt. Washington was due to a cyclonic 
movement of the winds which extended i the height of 6000: 
feet, or was due to a cyclonic movement of the winds which 
was confined to a lower stratum of the aloud From 
Plate II accompanying my tenth paper we see that the fluctua- 
tions of the barometer on the top of Mt. Washington are often 
quite unlike those at the base (which is 3387 feet below the 
summit, and 2898 feet above sea-level), and the fluctuations are 
‘sometimes greater in amount. From the plate accompanying 
this paper we also see similar differences between the barome- 
tric oscillations on Mt. Washington, and those at stations in its 
- vicinity near sea-level. According to theory, the fall of the 
Seagal during a me storm near sea-level should be to 
he fall on the top of Mt. Washington (the other elements 
which affect the result being supposed to be the same), in the 
ratio of the mean pressures at the two stations, i. e. as 29° 98 to 
23°63 or nearly as five to four. Hence we see that on the sum- 
mit of Mt. Washington there are frequently cyclonic move- 
ments of the wind which are more violent than those at inferior 
elevations, and this explains in! part the anomalies shown in 
table V. But these anomalies are partly due to the fact that 
the barometric minima on Mt. Washington generally occur 
later than they do at sea-level. In several of my former papers 
I have dwelt upon this subject, and the same fact is clearly 
indicated by the accompanying plate. The average date of 
minimum pressure on Mt. ashington is more ‘than eight 
hours later than it is at sea-level; and there are frequently 
secondary minima on Mt. Washington which do not occur at. 
sea-level or only in an inferior degree. Hence it results that 
when the barometer on Mt. Washington stands at its lowest 
point, the barometer at sea-level has “generally risen above the 
preceding minimum one or two tenths of an inch, and occa- 
sionally four tenths of an inch ; and at the time of a secondary 
minimum on Mt. Washington, ‘the barometer at sea-level may 
have risen three or four tenths of an inch, or even five tenths of 
an inch more than it has risen on Mt. Washington. Thus on 
Jan. 15.1, 1875, when the barometer on Mt. Washin ngton was 
oo 2 et its lowest eh the barometer at sea-level had already risen 
