INSTRUOriONS aiVEI^ IN SCHOOL OP FORESTRY. 163 



dry that the winds carry it to a great distance. The smallest obstacle, 

 such as a little hillocli of soil, a tree, some tufts of broom, or of bent 

 grass (arundo arenaria) are enough to stop the sand ; it then 

 accumulates much faster and forms larger heaps than when deposited 

 by the waves, as the winds blow for a long time in the same 

 direction. Such is the origin of the Dunes, of which the height and 

 form vary like the conditions which have created them. Some are 

 to be found from 20 to 30 and even 50 or 100 metres in height. 



" It is by a mixed system of wicker-work barriers and reboisement 

 with maritime pines that the ini'oads of the sand which threatened 

 the neighbouring communes have been nearly everywhere arrested ; 

 and it is one of the triumphs of the Corps des Fonts et Ghaussees, to 

 whom the Government entrusted this great and important work, and 

 who have not only completed the undertaking, but they have by 

 degrees improved and simplified the work and operations required, 

 and have thus brought it within the power of any one to carry on 

 similar work elsewhere." 



To render intelligible to those who are unacquainted with the 

 more advanced system of forest management followed on the 

 Continent of Europe, the additional statements to be made, it may be 

 well for me to state, that it differs considerably from the arboriculture 

 which is generally practised in Britain, and from the Jardinage, and 

 Sartage, practised in British Colonies and in the United States of 

 America, and to supply here the following information in regard to it ; 

 and to repeat in substance what I have already said in speaking of 

 the culture of the Scotch fir : 



In the general management of forests on the Continent, in accord- 

 ance with the most advanced forest science, three things are aimed 

 at, and so far as practicable each is sought to be attained without 

 detriment to either of the others : the sustained production, natural 

 reproduction, and progressive amelioration of the forest. In prosecu- 

 tion of this there is determined, according as quantity, quality, or 

 pecuniary profit may be mainly sought, at what age the trees shall 

 mostly be felled. This in French is spoken of as the exploitability 

 of the woods. But before this age is attained there are several 

 successive thinnings executed, each with a special object, in accordance 

 with which it has a specific designation. 



The wood being the product of natural reproduction, or self-sown 

 seed, there is often required a thinning out of the seedlings . This is 

 known as the cou,pe d'ensemencement. 



There may be required one or more successive thinnings as the 



