2 20 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



the tides. The flowing tides hold up the fresh water from the 

 rivers, and so enable it to deposit its silt, and thus by degrees 

 the ground level is raised, and in consequence the characteristic 

 tidal vegetation is after a time replaced by trees of the ever- 

 green or deciduous forests. Lastly, across the Bay of Bengal, 

 there are the primeval forests of the Andamans and Nicobars, 

 with the species of " padauk " that is not found on the main- 

 land, and where ocean currents have brought the seeds of 

 exotic trees to flourish on the island shores. 



We have now indicated the general sequence of forest 

 vegetation from the snow-line to the sea, and may next consider 

 the effects of this vegetation in regulating the water-supply to 

 the plains below. On the upland meadows, on the junipers, 

 and on the birch and fir woods the greater portion of the annual 

 precipitation falls in the form of snow. The summer is short 

 at these elevations, but the snow melts quickly under the direct 

 rays of the sun. The resulting moisture is readily absorbed 

 by the porous turf, by the mosses, and by the rich vegetable 

 soil, yet there is always the danger of vast accumulations of 

 melting snow sliding down the steep slopes and carrying 

 everything before them, unless barriers are erected to prevent 

 these mishaps. The forest-trees provide such barriers, formed 

 of living piles, which sustain the weight of the snow till it gently 

 melts away ; the birch trees are bent with the weight they have 

 to sustain, and the firs are scored with wounds from many a 

 boulder that might, without such hindrance, have provided 

 the commencement of a disastrous avalanche. 



On the lower hills the rainfall is more to be dreaded than the 

 snow, which occurs less frequently. Here the protection of the 

 forest is required to prevent the slopes from being scored by the 

 action of intermittent torrents, which are powerful enough not 

 only to remove the surface soil but to cut deep ravines into the 

 hillsides. Fire and excessive grazing soon destroy all protective 

 vegetation, and the next stage brings discomfort to the resident 

 in the plains below. It has been truly said that the forester 

 does not object to seeing cattle upon a thousand hills ; it is the 

 thousand cattle on one hill that embitter his life by making his 

 work ineffective. 



But not only does erosion of the unprotected mountain side 

 bring distress to the population of the plains by drying up the 

 permanent water-supply, by covering the fields with sand and 



