CHAP. XXXIV.] ALLUVIAL PLAIN. 255 



has lately removed the doubts of De Candolle re 

 specting this measurement, which was taken above 

 the dilated base, for that was no less than 200 feet 

 in circumference. In this stem there would be 5352 

 rings of annual growth, if one line a year was taken 

 as the average growth, the deposit of wood becoming 

 always much smaller in trees of great age ; but Zuc- 

 carini, in his estimate, thinks it may be safer to 

 assume 1 6 line as the average, which would even 

 then give the age of 3512 years for this single tree. 



The great number of crescent-shaped lakes to the 

 westward of the Mississippi, which formerly con 

 stituted bends in its ancient channel, are also monu 

 ments of the antiquity of the great plain over which 

 the river has been wandering. Darby, the geogra 

 pher, observed that, in the steep banks of the Atchafa- 

 laya, there are alternations of the blueish clay of the 

 Mississippi and of the red ochreous earth peculiar 

 to Bed River, proving that the waters of these two 

 streams once occupied alternately considerable tracts 

 below their present point of union.* Since their 

 junction (an event, the date of which is unknown), 

 the waters and sediment of the Red River and Mis 

 sissippi have been thoroughly mixed up together, 

 before any deposition of their mud takes place in the 

 lower country. It is evident, therefore, that, when we 

 arc enabled, by geological observations such as those 

 of Darby, to distinguish the older from the newer 

 portions, even of the modern alluvial plain, we may 

 obtain more aid in our chronological computations 



* Darby s Louisiana, p. 103. 



