244 Second Report of the Meteorological Committee of 



shew — in which the interval embraced by the observations is 

 divided, not as usual into lunations from full to full or from new 

 to new Moon, but into periods marked by the moon^s passing 

 from south to north of the equinoctial. By this division the 

 effect (if any) of the moon's change of declination compensates 

 itself, and leaves the solar effect in evidence. The cause of the 

 prominence thus given to this part of the sun''s agency, appears 

 to lie in the length of its period compared with the moon''s, 

 which gives time for the waters of the whole ocean to accom- 

 modate their general level to the actual force, by bodily trans- 

 fer from one part of the globe to another, and by assuming, at 

 each instant (what the tides of short period have never time to 

 do), very nearly the figure of equilibrium due to this particu- 

 lar modification of the disturbing forces. 



Observed Mean Positions of the Mid-water mark on the Float of the 

 Tide-gauge at Simo9i's Bay^ during successive intervals of tJie 

 Moon's Transit from North to South of the Equinoctial, 



At the meetings of the Institution of Wednesday Septem.- 

 ber 3, and October 1, Sir J. Herschel stated that he had exa- 

 mined the Meteorological Journal kept at the Pert-Office by 

 Mr M'Cleod, under the direction and superintendence of Cap- 

 tain Bance, during 58 months, commencing with October 15. 

 1828, in which are registered the heights of the Barometer with 

 the temperature of the instrument, for the hour of 9 a.m., noon, 

 and 3 p. m., with the usual notices of wind and weather, and 

 that having reduced and interpolated them by graphical projec- 

 tion, he had been led to the following conclusions : — 



1st, That the atmospheric pressure at Cape Town is subject 

 to a considerable and very regular annual fluctuation, amount- 

 ing (when reduced to a temperature of 32° Fahr.) to 0.287 in. 



