2C2 OX TREE MEASUREMENTS. 



XXXI. On Tree Measurements* 



Sir R. Christison suggested that the members of the Society 

 might with great advantage undertake a systematic series of 

 observations on tree measurements, with the view of obtaining a 

 more trustworthy estimate, than is now accessible, of the rate and 

 limit of growth, under various circumstances of soil, elevation, 

 exposure, etc., of the principal species of forest trees cultivated in 

 Scotland. His attention had been turned to the want of informa- 

 tion on this subject in the course of an inquiry which he had 

 from time to time attempted, to test the validity of De Candolle's 

 theorem as to the growth of trees ; which, that eminent authority 

 maintains, increase the radius of their trunk after the first forty 

 or fifty years, with great uniformity, if measured by decades in- 

 stead of annually, so long as they flourish, even for several 

 centuries. Repeated opportunities of examining the trunk sections 

 of old trees grown in Scotland and in Canada prove that De Can- 

 dolle's theorem is totally inapplicable to the forest trees of this 

 country and those of North America, and indeed render this very 

 convenient theorem extremely doubtful anywhere except in rare 

 exceptions. In all instances yet examined the width of the annual 

 layers of wood was found to decrease materially at intervals, till 

 at last it was sometimes reduced to a third, or even a fourth only, 

 of the width at the fortieth or fiftieth year, though the wood was 

 everywhere sound, and the trees ascertained in some cases to have 

 been healthy and vigorous to appearance before being cut down. 



Desiring to obtain other information from the ascertained rate 

 of increase in girth of living trees in a given time, it appeared 

 that very little information of the kind now exists, and that which 

 is available is untrustworthy, owing to the loose irregular way in 

 which the measurements have been taken. But for this neglect 

 of method, the extensive set of measurements of forest trees, 

 collected by the Highland Society in 1867, might now furnish 

 valuable results by comparative measurements. A few data are 

 available for the purpose. But by far the greater number are use- 

 less, because the measurements have been taken in their instances 

 too low, or at irregular heights from the ground, or without 



* Remarks made by Sir Robert Christison, Bart., at the Annual General 

 Meeting, 6th November 1877. 



