evisting Physical Causes during stated Periods of Time. 219 
velocity is partially neutralized by impinging against stratum 
_ From the following particulars of the deltas of the Ganges and 
Po, it would appear that they are similarly situated to the Missis- 
sippi. “An Artesian well at Fort William near Calcutta, in the 
year 1835, displayed at a depth of 50 feet a deposit of peat with 
a red-colored wood similar to that now living. At 120 feet clay 
and sand with pebbles were met with. At the depth of 350 feet 
a freshwater tortoise and part of the humerus of a ruminant were 
found. At 380 feet, clay with lacustrine shells was incumbent 
upon what appeared to be another dirt-bed or stratum of decayed 
wood. At 400 feet they reached sand and shingle.’* 
In the delta of the Po, a well bored 400 feet failed to penetrate 
the modern alluvial deposit ; very near the bottom it pierced beds 
of peat, similar to those now forming. The coarser particles of 
mud which have already passed the mouths of rivers may con- 
tribute to the marine or fluvio-marine deposits forming outside 
deltas; but this can only be to a limited extent, as the great bulk 
of the mud is far too fine to settle near the coast. Little material 
Contingences, and-also for their organic contents. 
et us now turn to fig. 9, which exhibits Sir Charles Lyell 8 
transverse section of the channel and plains of the Mississippt, 
an : 
ial levée; d, d the banks and plains; m, m the swamps of the 
Mississippi. “The bankst are higher than the bottom of the 
sw 
* Lyell, Joe. eit inci 267-270. 
; . cit. p. 248; and Principles, p- : ‘ : 
There is a instar po aes of the Wile bd its banks published in the fourth vol- 
byl of the Quarterly Journal of the Geological Society, Pp. 344, but communicated 
¥ Lieut, Newbold in 1842. 
