ON TREE MEASUREMENTS. 263 



mention being made whether the place of measurement was free 

 from the fallacy arising from the conoidal base of large trees on 

 the one hand, or the swelling on the other hand below the giving 

 off of the first great branches. It is plain, for example, that if a 

 tree be measured at 3 feet from the ground, just above its basal 

 swelling, a measurement, say twenty years later, at the same 

 height, when the upper end of the swelling may have attained the 

 height of 4 or even 5 feet, will give a very exaggerated account 

 of the growth, in the same period of time, of all the comparatively 

 cylindrical pai't of the trunk above. To avoid this source of 

 fallacy, it is well to record the measurements at 3, 4, 5, and 6 

 feet from the ground ; but when only one measurement is taken, 

 it should be at 5 feet — unless when the tree branches low, in 

 which case the narrowest part of the trunk ought to be the place 

 of comparative measurements. It is seldom that the summit of 

 the conoidal swelling at the base rises higher than 5 feet, unless 

 occasionally in trees of very gi-eat age. In the yew alone there is 

 usually no basal enlargement as it attains great age. In all the 

 old yews I have seen, and in every drawing but one, the girth at 

 the ground at 200, 500, and even 1000 years, is not greater, but 

 on the contrary rather less, than at any place higher up. 



What seems to be wanted therefore is, the measurement of 

 trees, young, middle-aged, and old, at 5 feet from the ground, 

 except in the case of the yew, which may be taken at 1 foot only. 

 Mention should also be made of the elevation to which the basal 

 swelling reaches, and also at what height the swelling begins 

 which supports the lowest considerable branches. It is certain 

 that in the course of five years comparative measurements made 

 under these conditions would yield important information, pro- 

 vided the soil, elevation above the sea, particular exposure or pro- 

 tection, and other circumstances known to affect tree life, be at 

 the same time accurately recorded. 



