THE EARTH'S SURFACE ICE ACTION. 63 



glacier by wind, and all such auxiliaries to quantity 

 must be subtracted from the real amount of actual 

 work done by a glacier on its bed. 



Ice work is somewhat similar to sea work, in that 

 both agents are principally mechanical workers ; yet 

 marine action appears incapable of performing as 

 much denudation on ice-dressed rocks as elsewhere. 

 This is very apparent west of Spiddal, Co. Galway, 

 and in other places on the coast of Ireland, where 

 ice-dressed rocks have resisted the action of the sea, 

 although exposed thereto for ages. This would 

 appear to be due to the ice having come after 

 meteoric abrasion, and removed all the rocks and 

 debris that the latter force had loosened, and left ready 

 to be quarried and carried away; also to its having 

 ground the remainder into smoothly-rounded forms, 

 over which the waves would sweep with little effect, 

 therq being few roughnesses or abrupt inequalities to 

 offer resistance, and to afford them a handle by which 

 to work. Subsequently, but prior to the sea being 

 capable of executing any great quantity of work, the 

 rocks would again be exposed to atmospheric influ- 

 ences to open up the cracks and joints. The action 

 of ice would, after a time, even render the rock less 

 susceptible to itself, for when the loosened portions 

 of the rock are gone, the pressure and friction of the 

 glacier would be calculated not only to smooth and 

 polish it, but also to harden what remained, as hap- 



