3i8 Mr. W. S. Jevons ua the Semidiurnal 



9. But, to inquire more precisely what effect the daily varia- 

 tion of humidity will have upon the barometer, I refer to the 

 following Tables containing the average results of twenty-six 

 series of hourly observations undertaken by myself in Sydney, 

 at monthly intervals during the years 1855, 1856, and 1857. 



Table showing the daily variation of the iNIeteorological Elements 

 at Sydney, New South Wales. 



The above results nearly correspond with those derived from 

 hourly observations uninterruptedly carried on for eight years at 

 the Royal Observatory of Hobart Town, Van Diemeu's Land, 

 the evaporation, however, not being there determined. 



It is seen that in Sydney the maxima of the barometer occur 

 at 9 A.M. and 10 p.m., and the minima at 4 p.m. and 3 a.m. 

 These changes of the barometrical pressure, as well as the corre- 

 sponding changes of the various elements from which an expla- 

 nation might be sought, arc shown below. 



