132 NATURAL HISTORY OF SCOTCH FIR. 



hazles, elders, cornels, etc. ; the last, to perches and poles, from which 

 the lower branches have fallen through want of nourishment. 



To resume then our account of the instruction given in the School 

 of Forestry at Nancy, in regard to the exploitation of a forest of 

 Scotch fir. 



" In countries in which this tree, pimcs sylvestris, is very common, 

 they do not allow it to become aged. In effect the annual increase 

 of forest masses of this tree attains its maximum when it attains 

 the age of 60, 70, or 80 years ; then, after maintaining this for some 

 20 years, it begins to diminish with the advance of age. When then, 

 the primary object is to procure firewood, it is best to fix the revolution 

 cycle, or crop, at from 80 to 90 years. And this may be worth 

 attending to in countries in which this is the perdominating tree ; 

 but even in such a case, parts of the forest should be submitted to 

 a more protracted revolution to get useful timber of good quality. 



" In France, where timber is more scarce than firewood, the State 

 cannot fail to profit by delaying the exploitation of the pine. At the 

 period of its maximum increase, its wood ia not of the best quality. 

 It is only at a later period of growth that the grain of the wood 

 becomes compact, thatjt becomes charged with condensed resin, and 

 thus acquires the elasticity and durability which makes it valuable in 

 the construotiou of great works, and more especially for the navj. 

 hi view of such cousideratious, it would be well to apply to it a 

 revoluttoH of 120 years on lauds ou which its growth is active, and 

 not to exploit it till it have attained the age of from 140 to 160 

 years in dry soil of sufficient depth, like the siliceous sands in which 

 this tree delights, and acquires more especially the qualities which 

 fit it for employment in great works. 



" It must however, be remarked, that protracted revolutions have 

 this inconvenience, they compromise the fertility of the soil. After 

 a time, in the course of this protracted cycle, the pine forest no longer 

 constitutes a close mass, and it comes at an advanced age to be 

 converted into something like a glade. It follows that in course of 

 time it becomes covered with hurtful undergrowth, the wind disperses 

 the bed of dead leaves, and at the termination of the cycle the ground 

 finds itself sodden, dry, impoverished, and in circumstances moat 

 favourable for the multiplication of very hurtful lepidopterous 

 insects, the caterpillars of which only earth themselves in the 

 driest soils. 



" When then a cycle of 120 years or upwards is decided on, not 

 only should all deciduous broad-leaved woods, which naturally oome 



