268 EXACT PrtOGRESSlVE MEASUREMENT OF TKEES. 



all ; that no adecLiiate means were taken to secure that a subse- 

 quent measurement after an interval of some years should be 

 taken at precisely the same line as the first ; and that there was 

 sometimes reason to suspect careless and inaccurate observation. 

 In illustration of the last serious criticism, it may be stated that 

 when I applied for fresh measurements of certain somewhat 

 noted trees, whose trunks had been many years ago measured at 

 given levels from the ground, the information received in reply 

 made out that the girths indicated by the measurement of eleven 

 (liii'erent great trees all came to exactly so many feet, without 

 fractions. On account of these several reasons I had little satis- 

 faction in referring, for comparison in the present day, even to 

 the old measurements of Dr. Walker, or to the vast accumulation 

 we owe to the industry of Loudon, as displayed in his Arhorehcm 

 Britannicum, or to the long official catalogue published by our 

 Society in 1866. But on consideration it also appeared probable 

 that, by substituting for the coarse methods hitherto followed in 

 forestry something of the more delicate modes of inquiry pursued 

 in cultivating the sciences, there might be attained far greater 

 nicety, exactness, certainty, and speed, and consequently results 

 of much more practical value. The experience of the last four 

 years has amply confirmed these expectations. 



It has proved that measurements may be made, in the case of 

 most trees even of large size, to the accuracy of the tenth or 

 even twentieth part of an inch, with confidence in their exact- 

 ness ; and that the trunk-growth of many trees is such as, by 

 following the system recommended, may supply in the course of 

 a single year, or even in three months only, results applicable to 

 immediate practical treatment. For proof I refer to several 

 papers which have appeared during the past two years in the 

 Transactions of the Botanical Society of EdinlurgJi, giving the 

 result of observations made in 1878, 1879, and 1880, in the 

 Botanic Garden and Arboretum, and in the woods of Craigiehall 

 and Oammo, near Cramond, on upwards of eighty trees, young 

 and old, and belonging to thirty species. The results thus ob- 

 tained are the following : — 



1. After the first measurement and marking, in the way to be 

 described presently, all subsequent observations are made with 

 great ease, certainty, and speed. 



2. There is no growth of wood in leaf-shedding trees during 

 the seasons of winter and spring. This, of course, might have 

 been readily foretold ; but it appeared right, nevertheless, to settle 

 the point by positive observation. 



3. There is no growth of wood during the same seasons in 

 evergreen trees. This result, for obvious reasons, could not have 

 been foretold with the same confidence ; and, in fact, when I 

 consulted a knot of able botanists on the subject, none of them 



