628 



MOUND EXPLORATION!^. 



Nor will size turiiish ii ,siue iiiid .satisliiftory iiidicatiou. We are there- 

 fore at sea, as yet, on this question, and must be until botanists take 

 hold of tlie subject and work out some better rule for determining the 

 age of trees than has bcretofore been given. Dr. Lai>liaui undertook a 

 few years ago to reach a conclusion on the point at issue by an investi- 

 gation of the trees of Wisconsin. The result as given by Dr. Foster ' 

 is as follows : 



By placing the i-dge of :i sheet ot pajier aeross a newly felled tree lu the direction 

 of the radius, one may with a .sharp pencil mark the thickness ot the several ring.s of 

 growth, and by measuring a nuiuber of such rings we may tind the average increase 

 of wood each year. It was thus that the items were collected for the following table, 

 showing the number of rings measured, their aggregate width, the average annual 

 growth thus found, and tlie number of years retiuired lor an increase of 1 foot in 

 diameter of a number of our common forest trees: 



(livit'lli of iialire foiTSt trees of TViiKonsin. 



A more thorough and systematic investigation of the annual growth of trees 

 wouhl lead to results of greater certainty ; but the measurements already made and 

 embodied in this table are sufficient to show that there can not bo any great age 

 assigned to the average trees of our present forests. 



It will be seen that it recjuires the lajjse of from tifty-four to one hundred and 

 thirty years for trees to iu(Tease their diameter 1 foot, and with the average of 

 the trees measured the time is less than one hundred years. 



Three or four feet diametei- is a large tree ; few exceed that size ; and hence we may 

 infer that few of the triM's now growing in Wisconsin can antedate the discovery i>f 

 this continent by Columbus. An occasional tree exceeds these dimensions, but they 

 are exceedingly rare. 



Perhaps the largest and oldest tree in the state is the one noted by the gov (^'U- 

 nR>nt stirveyor near Manitowoc, a white cedar 22 feet in circumference. My this 

 table it will be seen that this tree is one of the slowest growth, requiring one hun- 

 dred and twenty-three years to add 1 foot to its diameter. 



' Prelii..itoric Races, iip. 373-375 note and table. 



