114 



BAEOMETER. 



Proceedings of Amer. Philos. Society, vol. 

 ix., p. 283. 



Question of a Resisting Ether. From Mr. 

 Chase's paper on " Barometric Indications of a 

 Resisting Ether," space will allow us to extract 

 only his conclusions upon this head, without 

 entering upon the preparatory and incidental 

 discussions. Proceeding still from the St. He- 

 lena observations, Mr. Chase finds two sets of 

 differences : the first, between the mean hourly 

 barometric readings and the averages of the 

 barometer heights at 0, 1, 2, and 3 hours from 

 each high and low aerobaric tide ; the second, 

 between the former values and the hourly heights 

 as calculated from theory : the largest difference 

 in the first set is at 20 h , the least at l h ; in 

 the second, the largest difference (greatest theo- 

 retical error) is at 21 h , and the least at 5 h and 

 15 h . 



The author concludes that the results fur- 

 nished in these two sets of differences show the 

 operation of some cause from l h or 2 h to 15 h 

 inclusive (say, 2 p. >r. to 3 A. M.) tending to 

 reduce the barometric pressure, while for the 

 rest of the day the normal pressure is increased. 

 That this cause is not to be found in differences 

 of temperature, he thinks evident, because the 

 observations are already corrected for known 

 effects of temperature, and because the average 

 height of the thermometer from 2 h to 15 h 

 (61. V) corresponds very closely with the average 

 from 16 h to l h (61.66). The greatest unex- 

 plained reduction of barometric pressure is at 

 9 h ; the greatest increase, at 20 h or 21 h . All 

 these facts appear to the author to admit of 

 explanation on the hypothesis that the disturb- 

 ances are caused by the resistance of an ether, 

 this being supposed, as had been done by Fres- 

 nel, to be condensed by planetary attraction. 

 Amer. Jour, of Science, Sept. 1864. 



Aerial Tides. Led by the remarkable coin- 

 cidence already shown between the theoretical 

 effects of rotation and the results of baromet- 

 rical observations, Mr. Chase has extended his 

 researches, with a view of defining more pre- 

 cisely some effects of lunar action on the atmos- 

 phere : his results appear in a paper bearing 

 the title above. 



Sabine had shown that the moon produces a 

 diurnal variation of the barometer, amounting 

 to about .006 of an inch, and thus equivalent to 

 nearly l-10th of the average daily variation near 

 the equator. This would indicate a tidal wave 

 of rather more than one foot for each mile's 

 depth of atmosphere, or from 3 to 6 feet near 

 the summits of the principal mountain chains. 

 Evidently, the rolling of such a wave over the 

 broken surface of the earth may exert a very 

 Important influence on the atmospheric and 



magnetic currents, the deposition of moisture, 

 and other meteorological phenomena. 



There would appear to be also a much larger, 

 and hitherto unadmitted, weekly wave. M. 

 Flaugergues, indeed, extending his researches 

 through an entire lunar cycle(October 1 9th, 1 808, 

 to October 18th, 1827), was led to infer that, " in 

 a synodical revolution of the moon,the barometer 

 rises regularly from the second octant, when it 

 is lowest, to the second quadrature, when it is 

 highest, and then descends to the second oc- 

 tant ; " and that this general law is modified by 

 the moon's declination and its distance from 

 the earth, the barometer being higher in the 

 northern lunistice, and in apogee. The St. 

 Helena observations give somewhat different 

 results, and among other things show that there 

 must be two principal maxima and minima in 

 each month. The means of these hourly obser- 

 vations indicate the existence of waves which 

 produce in the moon's first quarter a barometric 

 effect of +.004 in. ; in the 2d quarter, of .016 

 hi.; in the 3d, of +.018 in. ; and in the 4th, 

 of .006 in. A difference between the diurnal 

 and the lunar aerial tides is, that when the 

 former are highest their pressure is greatest 

 the lunar action accumulating the air under the 

 meridian so as more than to compensate for its 

 " lift ; " while in the general fluctuations and 

 in the weekly tides, a high wave is shown by a 

 low barometer, and vice versa. The continual 

 blending of these heavy and light waves results 

 in prolonged oscillations, shown by the alternate 

 rise and fall of the barometer at intervals of 

 two or three days. 



Mr. Chase presents a table of barometric and 

 thermometric means at the moon's changes, 

 in which he has deduced the heights pf the 

 weekly aerial tides as, at full moon, . 0115 in. ; 

 at 3d quarter + .0065 in.; at new moon, 

 + .0005 in.; and at first quarter, +.0044 in.; 

 the daily tides of the same periods in order are, 

 .0054 in., .0087 in., .0064 in., and .0047 in. 

 The differences of the successive weekly tides 

 give us the amount of barometric effect for each 

 quarter ; and the average effect is more than 

 three times as great in the 2d and 3d quarters, 

 as in the remaining half month. As in the 

 ocean tides, there are two simultaneous waves 

 on opposite sides of the earth ; but these are 

 not of equal magnitude, the barometer rising 

 higher for the tide opposite, than for that be- 

 neath the moon's place. 



Mr. Chase finds evidences of a combination of 

 solar with lunar action, as in case of ocean 

 tides, producing spring tides at the syzygies and 

 neap tides at the quadratures. He generalizes 

 the facts relative to the attraction (luni-solar) 

 and the rotation waves, which have usually 

 opposite values, as follows : 



The luni-solar wave is descending from to 

 90, and from 180 to 270 ; ascending from 90 

 to 180, and from 270 to 360. 



The rotation- wave is ascending from 330 to 

 60, and from 150 to 240 ; and descending 

 from 60 to 150, and from 240 to 330. 



