1867.] 



Atmospheric Tide at Melbourne. 



501 



Years. 



Lunar-diurnal range in pressure of air. 





Full 

 moon. 



New 

 moon. 



First 

 quarter. 



Last 

 quarter. 



Mean for the 

 epoch of 



SyzygT. 



Quadra- 

 ture. 



1858- 59- 



1859- 60. 



1860- 61. 



1861- 62. 



1862- 63. 



in. 



o"i6526 

 •13682 

 •14017 

 •12969 

 •18316 



in. 



0*14492 

 •14272 

 •16672 

 •15270 

 •17752 



in. 



0^14627 

 •15817 

 •12792 

 •14664 

 •14802 



in. j in. 



0-17259 0-15506 

 ■15354 -13977 

 •14953 1 '15344 

 •19473 "14119 

 •13102 '18034 



in. 



0-15943 



•15585 

 •13872 

 •17068 

 •13952 



in. 



— 0*00437 



— -01608 

 + -01472 



— ^02949 

 + '04082 



Means 



•I 51022 



•156916 



•145404 



•160282 '153969 



•152843 



4- '001126 



The final result of this Table shows an average excess of 0"*001126 in 

 favour of the epochs of syzygy, hut an analysis of this value shows that for 

 three years the excess is in favour of the epochs of quadrature, while but 

 two years seem to confirm what we feel inclined to regard as the rule. So 

 much we are able to assert, however, that the lunar-diurnal range in pres- 

 sure of air at the time of the first quarter shows a minimum, and that near 

 the last quarter and new moon a maximum in this range seems to make 

 itself manifest. Although the evidence adduced in the case is not of 

 such a positive nature as that produced when treating on the question of 

 the increased pressure of air near the perigee, we feel nevertheless inclined 

 to believe some similar relation to exist between the atmospheric tides and 

 the moon's phases, as we know to be the case with respect to the oceanic 

 tides, and that a more rigorous inquiry into this question than we are able 

 on the present occasion to institute, will ultimately yield a result in strict 

 accordance with the theory of gravitation. 



Before concluding these researches I may be allowed to point out a fact 

 corroborative of the result arrived at when speaking of the difl:erence of 

 atmospheric pressure near the epochs of syzygy and quadrature. The mean 

 diurnal range resulting from the last inquiry amounts to 0"* 153301 ; but 

 on the former occasion we found this range to be 0"* 14954. The excess 

 of 0"'0037G, of which the lunar-diurnal range of the atmospheric pressure 

 is larger, when derived from the epochs of the moon's phases, than when 

 obtaining it by the periods of perigee and apogee, must be attributed to 

 the fact that in the latter case sixty-six periods of perigee were com- 

 bined with sixty-seven periods of apogee, giving a fair average result ; 

 while in the former forty-three epochs of perigee and but thirty-five of 

 apogee happened to coincide with the several phases of the moon, tending 

 in this way to raise the mean value of the lunar-diurnal range of the baro- 

 meter above that average. 



