1864.J 



407 



[Chase. 



The existence of the tidal law, which, as we have seen, should 

 produce differences in the respective ratios of .5, .866^ and 1, at 1, 

 2, and 3 hours from the mean tide, is shown in the following 



TABLE OF TIDAL DIFFERENCES AND RATIOS. 



By a partial interpolation for the true time of mean tide at St. 

 Helena, I obtain for the ratios of the means .557, .860, and 1, cor- 

 responding precisely with theory at 2h. from mean tide. The tables 

 furnish suggestive evidences of the effect of declination, the varying 

 tidal influence of attraction, when acting with and against rotation, 

 and the resistance of gravity to the tidal flow of air. 



The rationale of M. Flaugergues' second and third inferences thus 

 becomes intelligible ; the phenomena of ocean tides are connected 

 with those of the atmosphere, which are subject to fewer extraneous 

 disturbing influences, and can therefore be more easily investigated; 

 and the long-suspected obedience of the principal meteorological 

 changes to fixed natural and mathematical laws, is at length made 

 evident. 



There are, therefore, manifestly four important causes of barome- 

 tric disturbance : 1, rotation, with its quarter-daily phases of alter- 

 nate aid and opposition to the attraction and temperature-currents, 

 and of shifting the aerial particles to levels of greater or less density ) 

 2, variations of temperature and vapor ; 3, lunar attraction ) 4, solar 

 attraction. Among the subordinate causes, perhaps the next in 

 order of importance is, 5, resistance of the aether, which, according 



