DRAINAGE. 117 



fields of peat which cover hundreds and thousands of acres on 

 the mountain slopes of Ireland and Scotland may, notwith- 

 standing their elevation and inclined position, be considered 

 as actual lacustrine basins containing millions of tons of water 

 dispersed among their innumerable leaflets. The supera- 

 bundant water of these tracks of peat-mosses issues forth in 

 springs on the plains below." 



The protective action of a vegetable covering is 

 thus alluded to by Prestwich in his " Geology, 

 Chemical, Physical, and Stratigraphical," * page 

 136: 



" This surface soil, with its usual covering of herbage, serves 

 to protect the land from further degradation, and checks the 

 denuding action which would otherwise scour the surface after 

 every shower of rain. Instances have been adduced to show 

 how persistent are the features of such a surface. The posi- 

 tions of the many dolmens and other so-called ' DruidicaP 

 stones, so common on the downs of this country and in many 

 parts of France, shows that the level of the vegetable soil has 

 undergone little or no change since they were first erected. 

 The camp of Attila, situated in the great chalk plains of 

 Champagne, furnishes a well-known date, namely, A.D. 451. 

 Notwithstanding its more than fourteen hundred years, the 



* Keprinted, by permission, from " Geology, Chemical, Physi- 

 cal, and Stratigraphical," by Joseph Prestwich, M.A., F.R.S. 

 Vol. i. Oxford, Clarendon Press, 1886. Pp. 477. 



