Chase.] 



286 



[December. 



The mean of tlie above differences varies from the theoretical 

 mean, less than g ^'q q of an inch. If we take the mean of the ratios, 

 instead of the ratios of the means of the observed differences, the 

 coincidence is still more strikinsf. 



The calculated time for the above observed means, differs less than 

 20" from the actual time. 



Observed Means, 



Theoret. Difference of Time, 



Observed Difference of Time, 



•498625 -864625 1-000000 

 59^ 48'^ 119^ 40'^ 180' 

 60' C' 120' 0" 180' 



The varying centrifugal force to which the earth is subjected by 

 the ellipticity of its orbit, must, in like manner, produce annual tides. 

 The disturbing elements render it impossible to determine the ave- 

 rage monthly height of the barometer with any degree of accuracy, 

 from any observations that have hitherto been made. We may, 

 however, make an interesting approximation to the annual range, 

 still using the St. Helena records, which are the most complete that 

 have yet been published for any station near the equator. Com- 

 paring the mean daily range, as determined by the average of the 

 observations at each hour, with the mean yearly range, as determined 

 by the monthly averages, we obtain the following results : 



