TRANSACTIONS OF THE SECTIONS. 117 
On a Comanche Vocabulary. By R.G. Laruam, M.D. 
From the evidence of two scanty vocabularies, the Comanche language appears to 
be closely allied to that of the Shoshonie or Snake Indians. 
On the Origin of the Modern Greeks. By G. Finuay. 
On the Tasmanians. By H.B. Daviss. 
On the Africans of the neighbourhood of Bonny. By Capt. Brian. 
On the Inhabitants of Prince’s Island. By the Rev. J. FREEMAN. 
On the Inhabitants of Port Essington. By Mrs. Suort. 
On the Delta and Alluvial Deposits of the Mississippi, and other points in the 
Geology of North America, observed in the years 1845-46. By CHARLEs 
Lye.., W.A., F.R.S. and V.P.G.S. 
(A Discourse delivered at the Evening Meeting, Monday, Sept. 14, 1846.) 
The delta of the Mississippi may be defined as that part of the great alluvial plain 
which lies below or to the south of the branching off of the highest arm of the river 
called the Atchafalaya. This delta is about 14,000 square miles in area, and ele- 
vated from a few inches to ten feet above the level of the sea. The greater part of 
it protrudes into the Gulf of Mexico beyond the general coast-line. The level plain 
to the north, as far as Cape Girardeau in the Missouri, above the junction of the 
Ohio, is of the same character, including, according to Mr. Forshey, an area of about 
16,000 square miles, and is therefore larger than the delta. It is very variable in 
width from east to west, being near its northern extremity, or at the mouth of the 
Ohio, 50 miles wide, at Memphis 30, at the mouth of the White River 80, and con- 
tracting again further south, at Grand Gulf, to 33 miles. The delta and alluvial plain 
rise by so gradual a slope from the sea as to attain at the junction of the Ohio (a 
distance of 800 miles by the river).an elevation of only 200 feet above the Gulf of 
Mexico. 
Mr. Lyell first described the low mud-banks covered with reeds at the mouths of 
the Mississippi and the pilot-station called the Balize; then passed to the quantity 
of drift-wood choking up the bayons or channels intersecting the banks ; and, lastly, 
enlarged on the long, narrow promontory formed by the great river and its banks 
between New Orleans and the Balize. The advance of this singular tongue of land 
has been generally supposed to have been very rapid; but Mr. Lyell, and Dr. Car- 
_ penter who accompanied him, arrived at an opposite conclusion. After comparing 
the present state of this region with the map published by Charlevoix 120 years ago, 
they doubt whether the land has on the whole gained more than a mile in the course 
of a century. 
A large excavation eighteen feet deep, made for the gas-works at New Orleans, and 
still in progress in March 1846, shows that much of the soil there consists of fine 
clay or mud, containing innumerable stools of trees, buried at various levels in an 
erect position, with their roots attached, implying the former existence there of fresh- 
water swamps covered with trees, over which the sediment of the Mississippi was 
spread during inundations, so as slowly to raise the level of the ground. As the site 
_ of the excavation is now about nine feet above the sea, the lowest of these upright 
trees imply that the region where they grew has sunk down about nine feet below the 
sea-level. The exposure also in the vertical banks of the Mississippi at low water, for 
