332 



Mr. P. E. Chase on Aerial Tides, [June 16, 



and neap tides at the quadratures ; and I believe that the most important 

 normal atmospheric changes may be explained by the following theory : — 

 The attraction- and rotation- waves, as will be readily seen, have generally 

 opposite values, the luni-solar wave being 



Descending, from 0° to 90°* and from 180° to' 270°, 

 Ascending, from 90° to 180° and from 2/0° to 0° j 

 while the rotation- wave is 



Ascending, from 330° to 60° and from 150° to 240°, 

 Descending, from 60° to 150° and from 240° to 330°. 

 From 60° to 90° and from 240° to 270°, both waves are descending, 

 while from 150° to 180° and from 330° to 360° both are ascending. In 

 consequence of this change of values, besides the principal maxima and 

 minima at the syzygies and quadratures, there should be secondary maxima 

 and minimaf at about 60° in advance of those points. 



The confirmation of these theoretical inferences by the St. Helena obser- 

 vations appears to me to be quite as remarkable as that of my primary hy- 

 pothesis. If we arrange those observations in accordance with the moon's 

 position, and take the average daily height of the barometer, we obtain the 

 following 



Table of the Lunar Barometric Tides, 



Moon's 



Mean Daily Height of the Barometer at St. Helena, 

 28 inches + the numbers in the Table. 



Position. 



1844. 



1845. 



1846. 



1844-6. 

 Average. 



1 o 





 15 

 30 

 45 

 60 

 75 

 90 

 105 

 120 

 135 

 150 

 165 

 180 



•2621 

 •2650 

 •2707 

 •2691 

 •2625 

 •2682 

 •2667 

 •2593 

 •2595 

 •2677 

 •2712 

 •2710 

 •2621$ 



•3020 

 •3058 

 •3153 

 •3165 

 •3077 

 •3093 

 •3184 

 •3170 

 •3124 

 •3099 

 •3118 

 •3104 

 •3020 



•2701 

 •2693 

 •2707 

 •2688 

 •2688 

 •2783 

 •2800 

 •2721 

 •2686 

 •2691 

 •2715 

 •2735 

 •2701 



•2781 

 •2800 

 •2856 

 •2848 

 •2797 

 •2853 

 •2884 

 •2828 

 •2802 

 •2822 

 •2848 

 •2850 

 •2781 



This Table shows — 



1 . That the average of the three years corresponds precisely with the 

 theory, except in the secondary maximum, which is one day late. 



* Counting 9 from either syzygy. 



t The secondary maxima and minima should correspond with the daily maxima and 

 minima, which occur at St. Helena at about 4^ and 10^ a.m. and p.m., giving 0=60° a 

 maximum, and 9 = 150° a minimum. 



X Since the tabular numbers represent the semiaxes of the barometric curve, and not 

 the simple ordinates, the values for 0° and 1 80° are the same. 



