CORRYS WITH OR WITHOUT LAKE BASINS. 131 



a similar shape are frequent, on which account they 

 are passed over without much notice. Of the other 

 examples of cooses, if we give due allowance for 

 subsequent modification by meteoric abrasion, their 

 counterparts will be found in the cooms among the 

 larconnaught hills. One thing remarkable about these 

 cooms in the hills is, that although exposed for cen- 

 turies to meteoric abrasion, their floors are very similar 

 to those of the cooses now being formed by the sea. 

 In the hills, west of Lough Inagh, the floors of the 

 cooms slope outwards ; south of the Erriff valley they 

 slope to one side, while in the north part of the 

 Mweelrea mountains they contain deeps ; but the deeps 

 in the cooms and those in the cooses, as will hereafter 

 be stated, are not quite similar. Seemingly the con- 

 ditions most favourable for the sea excavating a coose 

 are as follow : First, The rocks on the coast should 

 lie nearly horizontal or dip inland. Secondly, The strata 

 must be traversed by breaks (whether master-joints 

 or faults) lying oblique to and crossing one another, 

 also joining into the coast-line. Thirdly, Alterna- 

 tions of rocks of various hardness or composition ; for 

 if rocks on a coast are homogeneous or nearly so, 

 marine action will probably denude the coast in more 

 or less regular sweeps or open curves. And, fourthly, 

 cross currents, in the sea, that will form eddies. On 

 an open seaboard, the denuding force must act more 

 or less uniformly; not so, however, in partly land- 



