Chase.] 39 g [June. 



ence, the barometer being- higher in the northern lunistice than in 

 the southern. 



0. That the action of the moon also varies with its distance from 

 the earth, the mean barometric height being less in perigee than in 

 apogee. 



The observations indicate the following average meridional fluctua- 

 tions of the barometer : 



1. In a semi-synodical revolution, 1 67 mm., or .065 in. 



2. Between the lunistices, 29 mm., or .011 in. 



3. Between perigee and apogee, 1.12 mm., or .0-14 in. 



The more recent and more complete observations at St. Helena 

 give somewhat different results, which serve to confirm the natural 

 a prior i conviction that there must be two maxima and minima in 

 each month. The means of three years' hourly observations indicate 

 the existence of waves, which produce in the first quarter a barometric 

 eifect of -f- .004 in.; in the second quarter of — .016 in.; in the 

 third quarter of + .018 in. ; and in the fourth quarter of — .006 

 in. ; results which appear to ba precine/^ accordant, in their general 

 features, with those which would be naturally anticipated from the 

 combination of the cumulative effect of the moon's attraction with 

 the daily wave of rotation, and the resistance of the tether. 



One peculiarity of this lunar-aerial wave deserves notice for the 

 indirect confirmation that it lends to the rotation theory of the daily 

 aerobaric tides, and the evidence it furnishes of opposite tidal effects, 

 which require consideration in all investigations of this character. 

 When the daily lunar tides are highest their pressure is greatest, the 

 lunar influence accumulating the air directly under the meridian, so 

 as to more than compensate for the diminished weight consequent 

 upon its "lift." But in the general aerial fluctuations, as we have 

 seen, and also in the weekly tides, a high wave is shown by a low 

 barometer, and vice versa. The daily blending of heavy and light 

 waves produces oscillations, which are indicated by the alternate rise 

 and fall of the barometer and thermometer at intervals of two or 

 three days. 



M. Flaugergues' observations at perigee and apogee seem to show 

 that a portion of the movement of the air by the moon is a true lift, 

 which, like the lift of rotation, must probably exert an influence on 

 the thermometer as well as on the barometer. On comparing the 

 daily averages at each of the quadratures and syzygies, I found the 

 difference of temperature too slight to warrant any satisfactory in- 

 ference; but a similar comparison of the hourly averages, at hours 



