Exact Measurement of Trees. 



171 



measurement of trees, it occurred to me as desirable to 

 ascertain, by means of a few trees of vigorous growth, 

 what is the rate of increase of wood at dijfferent periods of 

 the growing season. That season has been already found 

 to exclude the six winter months, from October to April, 

 equally for evergreen and leaf-shedding trees. It now 

 turns out, however, that, in our climate at least, the period 

 of growth of wood in an ordinarily good season is much 

 more limited. 



For this investigation I selected the Beech and Hungary 

 Oak among leaf-shedding trees, and the Sequoia, Araucaria, 

 and Atlas Cedar among evergreens, as in previous years 

 their trunks made an annual increment in girth of 1 

 inch to nearly 2 inches. The leading result may at first 

 create some surprise, viz., that the growth of wood in leaf- 

 shedding trees is confined in general to the three months 

 of June, July, and August. This will appear from the 

 following table, showing the girths on April 30, 1880, and 



the increments at the end of each successive month. The 

 Hungary oak is in some measure an exception, as in two 

 specimens there was an undoubted increase during tlie 

 month of May. The explanation is, that in 1880 this early 

 species was far advanced in foliage in the middle of that 

 month. The explanation of the generally narrow limit of 

 growth to three months, in spite of the favourable weather 

 last May and the still finer weather of September last, 



* In the end of July the foliage of this beecli was observed to be very thin, 

 owing to the extensive ravages of an insect. The observations for August 31st 

 were made for me in my absence by Mr Sadler. 



