DESTRUCTION OF TREES FOLLOWING CHARCOAL BURNING. 165 



having been exposed to the smoke of a brick kiln, from which they 

 were distant about 50 metres. 



" Invariably, when there is established a charcoal kiln in the 

 middle of a pinery, there are seen many circular ranges of pines, 

 which, through the effect of the fire and of the smoke, become 

 diseased, and they are not slow to dry up and perish. 



" These diseased and languishing pines become the cradle of 

 lignivorous insects which invade the forest throughout its extent, 

 if after having completed the work of destruction on the first trees in 

 which they were developed, they find themselves in the middle of a 

 miserable pinery, covered with mosses and lichens, the diseased con- 

 dition of which is so favourable to the propagation of these parasites. 



" Sometimes, however, the ravages of the lignivorous insects 

 manifest themselves notwithstanding that there are no charcoal 

 furnaces there, or these are far distant. In these exceptional cases, 

 in Sologne, the primary cause of the disease of the pineries can be 

 attributed only to the humidity or to the unfavourable nature of the 

 soil. 



" After the enfeebling influence which reduces the trees to an 

 impoverished condition, comes that of the vegetable parasites, which 

 carry on farther the enfeebling of the trees ; then come the insects 

 which seize possession of a prey incapable of offering any resistance. 

 According to some observations which I have made, it seems to me 

 that the lignivorous insects occasionally allow themselves to precede 

 those which betake themselves to the leaves, and buds, and young 

 shoots. If this be the case, one may be struck with the harmony 

 which ranges among the causes which tend to destroy a vegetable 

 from the time that it is in other than the normal conditions of 

 development. First, the soil produces its effect, then follow the 

 parasitic vegetables, and then the lignivorous insects, which, in arrest- 

 ing the circulation of the sap, bring the final cou}:) to the vegetable 

 attacked in its every part. 



" There come into operation in Sologne yet other causes to favour 

 the invasion of the pineries by insects at the periods of the first 

 thinnings. Great negligence is manifested in the operations carried 

 on with a view to giving to the pine the air and light favourable to 

 its development. 



" Pines growing too densely in their infancy famish one another, the 

 more vigorous destroy the more feeble, which become thus the food 

 of the insects ; at a later period, in the expectation that the expense 

 of the thinning will be covered by the faggots obtained, or by the 



