OSCILLATIONS OF THE BAROMETER. 25 



CHAPTER VI. 



182. From the foregoing chapter it appears that 

 the rise and fall of the annual tide must, by the com- 

 plications caused by the oscillations in latitude of the 

 culminating points of the solar and lunar tides, be in a 

 great measure concealed from superficial observation. 

 And that, therefore, the only observable effects, which 

 we can expect to find apparent as far as regards the 

 actual difference in the height of the water, is the 

 difference in the heights of the equinoctial tides men- 

 tioned in section 15; and also, owing to the variation 

 in the effects of lunar declination, this difference will 

 only be observable in the average of an extended 

 series of years. . And, besides this, a vast volume of 

 water might indeed oscillate backwards and forwards 

 between the northern and southern hemispheres 

 without making any apparent changes in the height 

 of the water along the coast lines. For the vis inertia? 

 tide is, in fact, raised by the pressure of the currents 

 against the banks of the ocean, and therefore the 

 tendency of such a tide is to cause the level of the 

 water to be higher along the shores than in the 

 central parts of the ocean; and the waters of the 



