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i 
1883.] asal 
{[Chase, 
disturbance, until the restoration of fair weather. The limit between 
anticyclonic and cyclonic tendencies, may be approximately assumed 
to be midway between the centres of high and low barometric pres- 
sure, All cloudiness or precipitation between the limit and the high 
centre, represents anticyclonic influence ; all between the limit and the low 
centre represents cyclonic influence. Local cyclonism sets in soon after 
precipitation begins, and the anticyclonic influence is thus partially hid- 
den ; but a critical examination of the weather maps will show that the pre- 
vailing currents of the region often continue to be anticyclonic until the 
rain or snow is nearly, or quite over. The evidences of storm breeding 
and stormy anticyclonism will be still more striking, if the changes of 
barometric pressure are studied in connection with the beginnings and 
subsequent growth of cirrus, cumulus, and nimbus clouds, as well as with 
the rainfall and the final breaking up of cloudiness. There are good rea- 
sons for believing that such study, systematically and thoroughly contin- 
ued under the direction and with the facilities of the Signal Service 
Bureau, would raise the successful verifications of the Washington forecasts 
to an average of at least ninety-five per cent. 
404. Pressure of Warm Air. 
Dr. Képpen, in discussing Ley’s work on the winds prevailing in West- 
ern Europe, announces four new theorems (Ann. hydr. und magnet. 
marit. meteor., 1882 ; cited by Setence, 499). 1. The air-currents deviate 
from the isobars towards the side of the lower pressure in the lower 
atmosphere, and of the higher pressure in the upper atmosphere, 2. An ex- 
cess of pressure exists upon the side of the warmer air-columns. 38. The 
depressions advance approximately in the direction of the air-current 
which has a preponderance of accumulated energy. 4. The state of mo- 
tion of a certain mean layer, of which the height is still to be determined, 
un in general be substituted for the onward movement of the vortex. A 
systematic comparison of these propositions with observations and with 
Blasius’s discussion of terial currents (Storms, chapter iii), may contrib- 
ute towards a fuller knowledge of stormy anticyclonism. It will also be 
interesting and instructive to see how readily Képpen’s theorems can be 
deduced from Ferrel’s laws. 
405. Solar-Barometric Viriatls. 
The first physical paper which I communicated to the American Philo- 
sophical Society (Proc. A. P. S., ix., 283-8) was based on virial considera- 
tions, but the discussions of Clausius had not prepared the way for their 
general acceptance. Accordingly, the method of treatment was so new, that 
many persons looked upon the results merely as curious and, perhaps, ac- 
cidental coincidences, The foregoing relations of virial influence to time 
of rotary oscillation enable us to reach the same results in a more sim- 
ple way. 
The mean barometric fluctuations, both daily and annual, may be re- 
