and the Mecms of ascertaining it. 881 



adduced of it, — that of the Baobab, which Adanson has proved, 

 by ingenious and plausible calculations, to be 5150 years old, and 

 that of the Taxodium (Cupressus disticha, Lin.), which analo- 

 gous reasoning might induce us to beHeve was even older. (See a 

 notice of these trees by Mr Alph. D. C. Bibl. Univ. April 

 1831.) Other examples, less worthy of notice, seem to confirm 

 the idea, that there are at present some trees in the world of 

 immense antiquity, witnesses, perhaps, of its later physical revo- 

 lutions. We can easily conceive that errors may happen in cal- 

 culations of this kind, and that they cannot be considered as 

 the expressions of exact truth, till examples of this vegetable 

 longevity are multiplied to such an extent as to support one 

 another *. I have been engaged on this subject for a consider- 

 able time, as appears from the publication of the Principles of 

 Botany, inserted, in 1805, in the first volume of the Flore Fran- 



• On the Growth of Timber. — In the year 1827, a large lot of hemlock tim- 

 ber was cut from the north-eastern slope of East Rock, near New Haven (in 

 America), for the purpose of forming a foundation for the wharf, which bounds 

 the basin of the Farmington Canal on the east. While inspecting and mea- 

 suring that timber at the time of its delivery, I took particular notice of the 

 successive layers, each of which constitute a year's growth of the tree ; and 

 which in that kind of wood are very distinct. These layers were of various 

 breadth, indicating a growth five or six times as full in some years as in 

 others, preceding or following. Thus, every tree had preserved a record of 

 the seasons, for the period of its growth, whether 30 years or 200, — and what 

 is worthy of observation, every tree told the same story. Thus, if you began at 

 the outer layer of two trees, one young and the other old, and counted back 

 20 years, if the young tree indicated, by a fuU layer, a growing season for that 

 kind of timber, the older tree indicated the same. My next observation was, 

 that the growing seasons clustered together^ and also the meagre seasons, came iu 

 companies. Thus, it was rare to find a meagre season immediately prece- 

 ding or following a season of full growth, — but, if you commenced in aclustre 

 of thin and meagre layers, and proceeded on, it gradually enlarged and swel- 

 led to the maximum, after which a decrease began and went on, until it ter- 

 minated in a minimum. 



A third observation was, that there appeared nothing like periodicity in the 

 return of the full years, or the meagre, but the clusters alternated at irre- 

 gular intervals ; neither could there be observed, in coinparing the clusters, 

 any law by which the number of years was regulated. 



I had then before me, therefore, two or three hundred meteorological tables^ 

 all of them as unerring as nature ; and by selecting one tree from the oldest, 

 and sawing out a thin section from its trunk, I might have preserved one of 

 the number to be referred to afterwards. It might have been smoothed on 

 the one side by the plane, so as to exhibit its record to the eye with all the 

 distinctness and neatness of a drawing. On the opposite side might have been 

 minuted in indelible writing, the locality of the tree, the kind of timber, the 

 year and month when cut, the soil where it grew, the side and point which 

 faced the north, and every other circumstance which can possibly be supposed 

 ever to have the most remote relation to the value of the table in hand. The 

 lover of science will not be backward to incur such trouble, for he knows how 

 often, in the progress of human knowledge, an observation or an experiment 

 has lost its value by the disregard of some circumstance connected with it, 



