132 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



eighty, or one hundred years, it is clear that the stems should be 

 thinned out gradually but a little more freely, so that the rate of 

 growth in thickness may not become too slow. 



Given, for instance, a crop composed of 600 good dominant 

 stems per acre, with an average diameter of 6 inches, by the 

 time the stems are 12 inches thick there should be no more than 

 24:0 per acre ; when they are 16 inches there may be 140 to 160, 

 and when they are 20 inches there may be 100 to 120. The 

 gradually decreasing severity of the operation thus becomes plain. 

 While we remove perhaps half the stems when they are 4 to 6 

 inches thick, we take out no more than one-tenth when they have 

 attained 20 inches. In any case the operation should be frequently 

 repeated, say, every five or six yeais, so as to avoid anything like 

 heavy fellings or the opening of the canopy. The true forester, 

 imbued with the sentiment of the forest, going to work with 

 prudence, will let his eye wander among the ci'owns continually, 

 but will only take out one here and there, not one of the best nor 

 one that is practically suppressed, for suppressed trees have their 

 utility. The term " selection thinning " has been applied to such 

 an operation as this, and has also been objected to dft the ground 

 that selection means the removal of the biggest. The objection 

 is invalid, since the essence of selection lies not so much in the 

 size of the trees as in the difi'used nature of the felling. 



The figures given above can evidently not be taken as the 

 measure of the operation in all cases. The forester has to find 

 this measure on the ground, for it will vary with the activity of 

 vegetation, with the state of the crop, and with the periodicity of 

 the thinnings themselves. Many owners would like to know how 

 to set about finding this measure. Given a young planted pole- 

 crop hitherto untouched, containing 1400, 1600, or even 1800 

 dominant stems per acre, with their crowns shooting up vigorously 

 to the sky, dominated stems may be neglected. It is easy to find 

 the number of stems per acre, since a square of 22 yards side 

 is the tenth part of an acre. Suppose there are 1 60 stems, and 

 they average 12 inches girth, they are too close, and too equal 

 among themselves, to prosper for long ; but what is the measure 

 of prudence ? When the stems are twice as thick, there should 

 remain hardly more than one-fourth of their number. If the 

 rate of growth gives fifteen to twenty years to attain that size, 

 the thinning may pass thrice over the ground during the period, 

 removing each time one-third or thereabouts of the crop. Here 



