Turning of the Wind. 113 



certain oscillations, the values of which are already known to 

 us, for instance, the horary variations ; in order to accom- 

 plish this object, I pursue the following course. As men- 

 tioned in the commencement of this paper, all results are 

 derived from hourly observations, so that each observation 

 will have to be corrected by a quantity equal to the amount 

 of oscillation due to the hour of observation. These are the 

 principles according to which Tables I. and II. — [vide pages 

 116-117, and Plate IV.] — have been constructed, and a dia- 

 gram showing the states of the meteorological instruments at 

 different periods of the revolution of the wind in a direct sense. 



Barometer. — -The barometer is highest at S.E., passes over 

 from rising to falling, continues to fall E., N.E., N., and 

 reaches its minimum when the wind blows from N.N.W. ; it 

 then passes over from falling to rising, continues to rise 

 through W.S.W. and S., and reaches its maximum at S.E. 

 again. 



Thermometer. — The temperature is lowest Avhen the wind 

 blows from S.E., and passes in S.E. from falling to rising, 

 continues to rise in E., N.E., N., and reaches its maximum 

 in N.N.W., when it passes over from rising to falling, and 

 continues to fall in W., S.W. and S. 



Aqueous Vapor. — The tension of aqueous vapor is least in 

 S.E., and rises in passing through N.E. and N. The western 

 hemisphere clearly shows local influences as the tension does 

 not decrease towards south, but increases again on account 

 of the great area of ocean towards the west and south. 

 Pressure of dry air coincides almost entirely with pressure of 

 air. 



Thus we have an indirect proof of the truth of the law of 

 the turning of the wind, furnished by observations of one 

 month only. 



The different meteorological instruments give us to under- 

 stand which current prevails at a certain time, a point which 

 it is sometimes very difficult, if not impossible, to do without 

 their help. 



It must be borne in mind that the results obtained from a 

 month's observations only, are greatly affected by disturb- 

 ances, because of the small number of observations that have 

 been made in some points of the compass. These deficien- 

 cies will be removed if we have to do with observations 

 extending over a longer period. In another place I shall bring 

 before the scientific world results deduced from one year's 

 observations, bearing on the same subject. 



Q 



