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IV. — Observations on the Annual and Monthly Growth of Wood in Deciduous 

 and Evergreen Trees. By the late Sir Robert Christison, Bart., and 

 Dr Christison. 



(Read 19th March 1883.) 



Having undertaken to continue the observations on the growth of trees 

 commenced by my father in 1878, and carried on by him with unflagging zeal 

 until a few months before his death in 1882, I give in the present paper the 

 measurements made by him in 1881, which he did not live to publish, and those 

 made in 1882 by myself. I shall also endeavour to point out the conclusions 

 which may be drawn from the whole series of observations, beginning in 1878, 

 arranging them under the heads of — 



I. Annual Observations. 

 II. Monthly Observations. 

 III. Influence of Weather on the Growth of Wood. 



Thus the deductions already arrived at by my father in this branch of his 

 investigations on the growth and measurement of trees will be again reviewed 

 and tested by the experience of two additional years. The other branches of 

 his subject, including his inquiry as to the proper mode of measuring the girth 

 of trees, the kind of information to be derived from such measurements, his 

 discussion of Decandolle's rule for estimating the age of trees by the annual 

 rings, the modes of doing so recommended by himself, and his description of 

 the Fortingall Yew, have been so fully treated in his earlier papers, published 

 in the Transactions of the Botanical Society of Edinburgh, as to require little 

 further elucidation. Very different is it however with the yearly and monthly 

 measurements. These can only become truly reliable after a prolonged series 

 of observations ; and even the present review of five years' experience must be 

 considered as to a considerable extent provisional and subject to correction. 



Before proceeding with the proper subject of this paper, it is advisable to 

 state that the observations and deductions in it rest entirely on the possibility 

 of making accurate measurements of the girth of trees. Previous to Sir 

 Robert's observations measurements of the kind were made in the vaguest and 

 most unreliable manner. It was reserved for him, in extreme but vigorous old 

 age, to make the simple discovery that such measurements could be depended 

 upon to within a tenth or even a twentieth of an inch, and that consequently 

 not only the annual but even the monthly increase could be accurately recorded. 

 I thought it was desirable however on taking up the subject as it dropped 

 from his hands to retest this question, and to ascertain whether my measure- 

 vol. xxxii. part i. h 



