660 Proceedings of the Royal Irish Academy. 



The last tide would have had its height augmented by the direction 

 and force of the wind, but this was counteracted by the high barome- 

 tric pressure. 



In conclusion, enough has been said to show the progress made in 

 accurate calculation, and the data upon which the effects of atmos- 

 pheric conditions may be estimated. A similar method may be applied 

 in the case of any other ports to which attention may be directed. For 

 instance, in the case of Kurrachee, it is found that the diurnal inequa- 

 lity is very visible, when the moon or anti-moon is south of the equator 

 at the instant of the transit, which occurs twelve hours previously. 

 The configuration of land and water affects the course of the tides 

 as certainly in the Indian as in the Atlantic Ocean ; everywhere it pro- 

 duces irregularities which cannot be ignored, when special tide-tables 

 have to be calculated. 



Plate XIX. represents the curves formed by the tides, as observed 

 by W. Parkes, E.G., at Kun-achee, and referred to in the Eeport of the 

 British Association for 1870. It shows, by means of the graphic pro- 

 cess at the foot of the diagram, the law of the "diurnal inequality," 

 for that place. Por an explanation of this process see these Proceed- 

 ings, antea, page 73. The law is this : when the moon is below the 

 equator, the lunar tides (combined with the solar) are highest, and 

 arrive at Kurrachee about twelve hours after the transit B. When 

 the anti-moon is below the equator, the anti-lunar tides (combined 

 with the anti-solar) are highest. The diurnal and semi-diurnal curves 

 are also shown. 



