72 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



basis, as above demonstrated, of a 2-inch check), and this would 

 have been but little when compared with the 6 milliards of tons 

 of water which the excess represented over the area concerned 

 (for a milliard equals looo millions). 



We may mention certain figures giving an idea of the material 

 carried down by floods. Thus, from the Pyrenees, in times of 

 heavy flood, for every cubic metre of water in the Garonne there 

 is li kilo of mud, in the Neste 13 to 16 kilos, in the Agly 

 up to 38 kilos ; from the Alps, where matters are much 

 worse, in the Glandon, i cubic metre of water will contain, 

 in similar circumstances, 150 to 160 kilos, and the Is^re has 

 123 kilos, which is equivalent, in 24 hours, to about 4,000,000 

 tons of silt for a flow of 380 cubic metres per second. 



7. The Formation of Plantations on Deep Peat. 



( With Plate.) 



By Donald Grant. 



The area on which the plantations have been established 

 comprises part of the estate of Corrour in Inverness-shire. They 

 occupy the stretch of land which extends from Loch Treig to the 

 river Spean. The plantations assume the form of a strip, vary- 

 ing in width from 100 yards to 500 yards, extending along the 

 West Highland Railway for two miles and a half, and following 

 the course of the river Spean for one mile and a half. The 

 boundaries consist of a deer fence along the inner limits of the 

 plantations, while the railway and the river Spean form the outer 

 boundaries. The land over the greater part of the planted area 

 is peat, ranging from 3 to 10 inches in depth on the knolls and 

 slopes, while it attains a depth of over 10 feet in the hollows and 

 more level places. On gentle slopes where the peat does not 

 exceed 10 inches in thickness the subsoil is a stiff clay with a 

 small proportion of white sand, while on the knolls and steep 

 slopes we find a loose gravel and sand which, to all appearance, 

 has been deposited in glacial times. The whole surface is 

 covered with a strong growth of herbage, the dominant plants of 

 which are the following: — Heather {Calluna vulgaris), bog 

 myrtle {A/yrica gale), flying bent {Molinia ccBrulea), mat grass 



