LECTURES ON BOTANY. 



407 



older layers of the latter split or exfoliate 

 when their tissue is no longer capable of dis- 

 tending, it would appear that there are no 

 assignable limits to tiieir growth ; that there 

 is no inherent cause, except the decay of vig- 

 or to which all organized bodies are subject 

 after the lapse of a certain period, why their 

 trunks, though originally a mile asiuider, 

 should not increase in bulk until they met, 

 and thus, as a fanciful though ingenious phi- 

 losopher once expressed his idea upon this 

 subject, cover the whole earth with '• ligneous 

 mountains." However specious in theory, 

 •we have no facts in favor of the probability 

 of such a result; and yet, to judge from their 

 bulk, some trees still existing in a healthy 

 state must have attained an enormous age ; 

 and, as when a ti-ee is cut down the number 

 of its years may be frequently ascertained 

 ■with a tolerable degree of certaintN', others 

 have been actually examined, which had 

 lived fi-om 1,200 to 1,C00 years. An atten- 

 tion to the age of trees, thus estimated, might 

 occasionally assist an antiquarian in his re- 

 searches, particularly, too, where the object 

 of his curiosity had outlived the history of 

 its date, or even passed the more extended 

 notice of tradition ; it has even been so em- 

 ployed. Of the above description of objects 

 are those extensive embankments in the 

 neighborhood oi' the Great Lakes of North 

 America, supposed to be the ruins of ancient 

 fortifications ; they are evidently the work 

 of a race different from that of the present 

 Indian tribes of those parts, who possess no 

 tradition of their origin, and seem to enter- 

 tain no opinion at aU respecting their use ; 

 they are regularly formed, and generally built 

 where a ravine or natural high bank strength- 

 ens the one side ; the walls are of eai'th, and 

 at present about five or six feet in hight ; at 

 some past period they may have been con- 

 siderably higher, as w-hen fu-st discovered 

 trees of very large size were growing upon 

 the mounds, indicating the lapse of a consid- 

 erable space of time since their erection. A 

 continued barrier of these works is said to e.x- 

 tend horn the northern side of Lake Ontario 

 toward the river district, and thence across 

 to the vast plains that reach the Mississippi. 

 Now fortifications, however rude, upon the 

 extensive scale on which these are de- 

 scribed by travelers, must be connected with 

 some very important feature in tlie history 

 of the co\intry they traver.se, and liave given 

 rise to various speculations concerning their 

 origin ; however, by counting the number 

 of woody circles in some of the trees just 

 mentioned, it has been ascertained that up- 

 ward of 450 years must have elapsed since 

 the works were abandoned, or rather since 

 Nature began to reiisscrt her dominion over 

 the usur])iiig ])ower of Man, at which period 

 it is but reasonable to suppose the trees in 

 question first rose from seed upon the spot 

 where they had so long flourished. This 

 calculation brings the possible date of their 

 origin nigh to an epoch which renders it far 



(7G7) 



from improbable that they were the work of 

 the ancient Mexicans, previous to the migra- 

 tion of that people southward, of which cir- 

 cumstance, it is well known, their tradition 

 at the time of the Spanish Conquest had pre- 

 served the memory. 



The age of a growing tree cannot be es- 

 timated by any known characteis ; and on 

 this account, and perhaps m some measure 

 owing to mankind being naturally fond of 

 the marvelous, some remarkable trees still 

 standing have had a most extraordinary age 

 assigned to them. It is true that various 

 rules for ascertaining it, founded upon careful 

 observation, have been laid down by certaui 

 naturalists ; but they are too arbitrary to sat- 

 isfy a rigid uiqnirer. Bosc and others have 

 allowed a foot in diameter for the growth 

 of a hundred years in the oak. Now there 

 are oaks growing in this country at the pres- 

 ent day, which, according to then- calcula- 

 tion, must be fiom 1,000 to 1,.500 yeai-s old, 

 then- trunks being from 10 to L5 feet m di- 

 ameter at the surface of the gi-ound. It is 

 not intended to deny the possibility of a ti'ee 

 attainmg this or even a much greater age, 

 but merely to show the fallacy of the grounds 

 upon which calculations are made. So long 

 as a ti-ee continues to live, there must be an 

 ainiual development of buds, and, however 

 thin it may sometimes be, an annual forma- 

 tion of wood. So long, therefore, as a tree 

 exists, a diametrical increase of the trunk 

 must take place in one direction or another, 

 if not generally; and that increase will be 

 proportionate to the number of buds unfold- 

 ed — in other words, to the quantity of fohage, 

 to the luxuriance of the ti-ee ; consequently, 

 when a tree has been flourishing in a perfect 

 state for some centuries, its diameter will be 

 proportionally greater than that of another, 

 which has had its branches broken by storms 

 or scathed by lightning, and its number of 

 buds thus diminished. I will adduce one 

 example of the fallacy of calculations made 

 upon the diametrical increase of the trunk of 

 a tree indicating its age. The Golenos oak, 

 a very remarkable one of its kind, which 

 gi"ew about lour miles fiom Newport in Mon- 

 mouthshire, was lelled for the use of the Navy 

 in the year 1810; the diameter of the trunk 

 of this tree, which was perfectly .sound in 

 every part, and at the time of its being felled 

 was in full luxuriance of growth, was nine 

 feet and a half Now, according to the above 

 mode of calculation, (a foot in a century,) 

 this tree would have been estimated, wliile 

 standing, to be 950 years old. I am not ac- 

 quainted with the preci.se number of itswoody 

 layers, but they were considerably under 

 450 — to the best of my recollection, 43(5 or 

 437. Here, then, had been a diametrical in- 

 crease of more than double the standard al- 

 lowed by Jiosc, which sufficiently shows the 

 little dependence tiiat ought to be placed 

 upon computations of the kind. Speaking 

 of this particular tree, we ought not to omit 

 remarking ui^u a curious, though not a sin- 



