570 



Correspondence. 



" Cliffs." 

 {b) " Tops mostly very uneven," 



(c) " Rarely through the highest 

 ground of a country, but mostly backed 

 by higher ground." 



Remakks, 



(i) In the west of Ireland the tops of 

 the escarpments are also " mostly very 

 uneven," except, perhaps, some of those 

 limestone escarpments in the Barony of 

 Burren, Co. Clare; but these are very 

 similar to the cliffs now being formed by 

 the sea in the limestones along that 

 coast. 



(c) If (for argument sake) we allow 

 that all cliffs were formed by the sea, it 

 would be nearly impossible that the 

 present sea-cliffs should run through the 

 highest ground of the country. For if 

 the land rose gradually the sea-action 

 would form a slope, a period of rest 

 being necessary for the formation of 

 cliffs ; and, therefore, to allow of the 

 cliff being in the highest ground, each 

 succeeding rest must, at least, be of 

 twice the duration of the previous one. 

 However, in spite of these conditions, 

 many of the headlands extending into 

 the Atlantic slope from the cliff inland. 



(d) Most, if not all, of the drift-sea- 

 cliffs have springs at their base ; so have 

 the previously mentioned cliffs in Aran- 

 more and Co. Clare. There are, also, 

 usually springs at the base of a cliff which 

 rise from a horizontal, or nearly hori- 

 zontal, master -joint. 



(e) The sea-cliffs on the west of Ire- 

 land are very irregular, never in anything 

 approaching a straight line or a wide curve. 



(/) On the west of Ireland there is 

 rarely a beach at the base of a cliff, 

 except, perhaps, when it is of Boulder- 

 drift, and even then not always. 



(7i) Not always. If there is a hori- 

 zontal, or nearly horizontal master-joint, 

 either above or below the sea-level, the 

 cliff is nearly sure to spring from it ; or 

 it may spring from a soft bed that occurs 

 under similar conditions. 



From the above remarks may it not be suggested that sound 

 conclusions cannot be drawn from observations made only among 

 peculiar rocks. If an observer will compare the work done by the 

 two dissimilar forces — marine and subaerial (including ice) denu- 

 dations — ^he will be surprised to find the results so very similar in 

 appearance. However, he should always bear in mind that the 

 subaerial agencies may work alone, when the marine agencies must 

 always be helped from above. Yours, etc., 



G. H. KiNAHAN. 

 CONNEMARA, NoV, lOth, 1867. 



"Escarpments." 



(f?) " Very rarely have the sea at their 

 foot, but often springs and watercourses." 



(e) " Often run in more or less winding 

 lines." 



"Cliffs." 

 (/) " Mostly a beach at their foot." 



(h) " Bases at the sea-level." 



