1867.] 



Atmospheric Tide at Melbourne. 



499 



Months. 



Lunar-diurnal range in Perigee minus lunar-diurnal range in 

 Apogee. 



1858-59. 



1859-60. 





IS6I-62. 



1862-63. 



]\Iean for 

 1858-63. 



May , 



Jamiaiy 



in. 



+0-0775 

 + -1146 



— "0251 



- -1279 



— "0148 



- -0128 

 + -1004 

 + -0287 



+ -1439 

 4- -0097 

 + "0815 

 + '0053 



in. 

 +0-1793 



- -2270 



- -0376 

 + -0786 

 + -0217 

 + -0144 

 + -1506 

 + -0320 



— -0296 



— -0083 

 + "0570 

 + -1217 



in. 

 + 0-1910 



+ '0220 

 + "C960 



— -0020 



- -0750 

 + '1070 

 + -0400 

 + '0160 

 + -0760 

 + -0805 



— 'OOIO 



- -0486 



in. 



— 0-0984 

 + '0676 

 + '0380 

 " -0044 

 + "ic+i- 

 + -0180 

 + -2006 

 + '0360 



— 'lOOO 



+ -0177 

 + -0727 



— -0410 



in. 

 + 0-1010 



- -1363 



- -0837 



- -0370 

 + -0587 



- '0417 

 + -1820 



- "0870 



+ "0020 



- -0270 

 + -0510 

 + -0060 



in. 

 + 0-09018 



— -03182 



— -00248 



— -01246 

 + -01904 

 + -01968 



+ -15477 

 + -00514 

 + -01846 

 + -01452 

 + -05224 

 + -00868 



^^f'^'^l Perigee., 

 epochs of J'^P''^^'^''- 



4- -04418 

 14 



+ -02747 



+ -03605 

 14 



13 



+ -02808 

 13 



13 



+ -00195 



13 

 14 



+ -02746 



66 Sum. 



67 Sum. 



The mean yalue of -f '02740 ^vas derived with due regard to the number 

 of epochs of apogee and perigee occurring in the whole period of observa- 

 tion, the total number of barometrical readings from which it was derived 

 being 720. 



There can hardly exist a doubt, after having examined the above re- 

 sults, that the lunar-diurnal range in pressure of air at the time of the 

 perigee exceeds the one at the apogee, a fact which is also in strict accord- 

 ance with theory. But it ought to be pointed out that during the months 

 of May, June, and July the reverse seems to take place, as is manifested in 

 every one of the five years of observation. Whether this bears any refer- 

 ence to the time of aphelion on the 3rd of July, and the time of the peri- 

 helion on the 2nd of January, we do not pretend to decide no\Y ; suffice it 

 to have directed the attention of those more immediately interested in in- 

 quiries of this nature to a matter replete with so much interest, but as yet, 

 comparatively speaking, scantily examined. The mean range for the 

 epochs of perigee and apogee is respectively 0"'1G327 and 0"*1358I, re- 

 sulting a general mean range of 0"' 149540. 



A similar plan to that just described was pursued, in order to ascer- 

 tain whether there existed any perceptible difference in atmospheric 

 pressure in the periods of syzygy and quadrature. The range of the 

 atmospheric pressure during a lunar day was determined for days of full 

 and change, and also for each of the epochs of quadrature separately, 

 and furthermore for the day preceding and following each of the several 

 epochs. Subsequently a mean value was derived by combining the daily 



