X EXPLANATION. 



Fig. 2. Represents high water at an equinox, either at new moon or at 

 full. If new moon, both luminaries would be in the direction of the upper 

 H, and if full, one would be in the direction of the upper and the other in 

 that of the lower ; but the height of the tides would be the same. The 

 low water would, in that case, revolve round the polar circles, and con- 

 sequently it would be continual low water at one of these j while the high 

 waters would revolve round the tropics. 



Fig. 3. Represents the action of the luminaries at the quarters, when the 

 high water of the sun coincides with the low water of the moon, and the 

 difference between high and low water is the least possible. 



Fig. 4. Represents high water at full or change at an equinox, and 

 when the sun and moon have the same declination. In that case both 

 tides of high water revolve round the equator, and the constant low water 

 is at each pole. 



Fig. 5. Represents the high water at full or change at the equinox, 

 where the moon has its greatest distance in declination from the sun ; 

 in which case the high water is at the dotted line, HH, between the 

 luminaries. 



Fig. 6. Represents the high water at the tropic, with the moon at its 

 greatest declination more than the sun ; and 



Fig. 7. Represents the same, with the moon at its greatest declination, 

 less than the sun. In figure 6 the high water is thrown without the tropic, 

 and in figure 7 it is thrown within. 



The tides in the atmosphere are affected in the same manner as those in 

 the ocean. 



These figures will afford some illustration in the extreme cases, and the 

 intermediate ones can be imagined from them. 



