Mr. P. E, Chase on Aerial Tides. 



155 



. -1. That in n synodical revolution of the moon, the barometer rises 

 regularly from the second octant, when it is the lowest, to the second 

 quadrature, when it is the highest, and then descends to the second 

 octant. 



2. That the varying declination of the moon modifies her influence, 

 the barometer being higher in the northern lunistice than in the 

 southern. 



The more recent and more complete observations at St. Helena 

 give somewhat different results, which serve to confirm the natural a 

 priori conviction that there are two maxima and two minima in each 

 month. The means of three years' hourly observations, indicate the 

 existence of waves which produce in the first quarter a barometric 

 effect of +"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 be precisely accordant, in their general 

 features, with those which would be naturally anticipated from the 

 combination of the cumulative action of the moon's attraction, with 

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



One peculiarity of the lunar-aerial wave deserves attention, for the 

 indirect confirmation that it lends to the rotation theory of the aero- 

 baric 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 heretofore, and also in the weekly tides which we are now con- 

 sidering, 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. Flangergues's 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 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 inference, but a similar comparison 

 of the hourly averages, at hours when the sun is below the horizon, 

 gave such results as I anticipated ; as will be seen by a reference to 

 the following 



Table of Barometric and Thermometric Means at the Moon's Changes. 



Moon's Phase. 



Full 



Third Quarter 

 New ......... 



First Quarter 



Average 

 Height of 

 Barometer, 

 in inches. 



Height of 

 Lunar 

 Weekly 

 Tides. 



28-270 

 28-289 

 28-282 

 28-286 



-•0115 



+ •0065 

 4- -0005 

 + •0044 



Height of 

 Lunar 

 Daily 

 Tides. 



Daily 

 Height of 

 Thermo- 



in. 



•0054 

 •0087 

 •0064 

 •0047 



67-67 

 61-68 

 61-65 

 61-63 



Thermo- 

 meter at 

 12 P.M. 



60-22 

 60-41 

 60-31 

 60-37 



Thermo- 

 meter at 

 4 A.M. 



59-787 

 59-824 

 59 716 

 59-823 



