ON THE COASTS OF IRELAND. 97 



The first column which deserves attention is the " mean of mean heights." The 

 progress of the numbers from Kilbaha to Limerick, as well as that from Dunmore 

 East to New Ross, show well the change of mean height in ascending a river affected 

 by current as well as by tide. Excluding these river stations, as also Buncrana and 

 Carrowkeel, which partake in some measure of the same character, we have a view 

 of the comparative mean heights of the sea on different parts of the coast of Ireland. 

 And here we have the remarkable result, to which allusion has already been made, 

 that the mean height of the sea round the northern half of the island, as referred to 

 the surface of stagnant water, is considerably greater than that round the southern 

 half of the island. The amount of this difference of height is believed by the officers 

 who directed the levelling operations to be much greater than can be explained by 

 any allowable error in the levelling. The heights on the eastern coast are also, per- 

 haps, a little greater than those on the western coast. I profess myself entirely unable 

 to explain on mechanical principles this result. 



In every instance except that of Castle Townsend, the mean height in large tides 

 is greater than that in small tides. Further allusion will be made to this in the 

 examination of the next table. I shall here only remark that I imagine this to be a 

 possible result of the shallowness of the sea, though theory has not yet reached so 

 far. 



MDCCCXLV. 



