176 MODEEN FOBEST ECONOMY. 



parts, and together with these, and with all besides, to 

 minister to the resultant end, so is it here ; and in the one 

 case as in the other, there is much besides the result 

 c«btained that is admirable in the adjustments by which 

 this is secured. The astronomer can not only tell what is 

 at present the relative positions of all the constituent 

 parts of the solar system ; he can also foretell what their 

 relative positions will be at any time in the future which 

 may be specified. I have seen a railway chart, by a glance 

 at which the directing engineer can tell what is, and what 

 at any hour or minute of the day will be, the relative 

 positions of all the regular trains under his charge. And 

 it is almost essential to the perfect working of the method 

 of forest exploitation now under consideration that the 

 Forester-in-chief, or some one connected with the adminis- 

 tration of the management of a forest, should be able to 

 tell what is the actual state of the forest in all its parts, and 

 what operations are going on in each of these, — but able also 

 to tell with proximate accuracy what will be the slate of 

 each of these parts, and in what form different parts will 

 be under exploitation, at any period of the future, within, 

 say, the next hundred years ! 1 have said with proximate 

 accuracy, because there are contingencies the effects of 

 which, with the amount of knowledge yet attained, cannot 

 be determined with absolute precision. But every year's 

 observations tend to reduce the measure of uncertainty 

 which is still inherent in the forecasts made of the future, 

 more or less remote. Meanwhile requisite corrections 

 are made by what may be considered a tentative process, 

 determined by experiment and observation. 



In the application to forest economy of the knowledge 

 which has been acquired in regard to the physiology of 

 arborescent vegetation, it is necessary, in order to securing 

 the greatest possible efficiency of this method of exploita- 

 tion, to have preliminary surveys made of the forest as a 

 whole, and of its several constituent parts, and to have the 

 results of these surveys embodied in charts or diagrams ; and 



