AMERICAN ASSOCIATION ADVANCEMENT OF SCIENCE. 639 
The author investigated the origin of these springs, by an examination 
of their ejecta — gas, water, and mud. The gas he found to be such as is 
produced by vegetable matter in its first stages of decay. The mud con- 
tains evidence of à mixed fluviatile and marine origin; while the water 
in which it is diffused, has the composition of sea-water changed under 
the influence of ferrugino-calcareous river mud, containing fermenting 
vegetable matter. 
The conclusion reached is, that the mud is the same as that which is 
deposited on the **blue clay bottom” of the Gulf, outside the bar, in a 
semi-fluid state. In its annual advance, the bar covers this mud stratum, 
which exists equally higher up the Passes; the increase in weight by 
vegetation, alluvion, etc., of the new formed land above, as well as that 
of the bar below the mouth, causes the bottom to bulge upwards at the 
points of least resistence, 7. e. in the deepest channel. 
Attention was called to the fact, that of all rivers known, the Mississippi 
is the only one exhibiting either mudlump action, or the peculiar narrow 
lands of bank, advancing rapidly towards deep water, which are known 
as **necks," and are obviously dependent on the mudlumps for their 
origin. It is therefore permissible to infer, not only that all the similarly 
Shaped alluvions above the head of the Passes, at least as far as the forts, 
have been formed by mudlump action, but also that the latter will cease 
so soon as the bar, in its advance, shall pass beyond the shelf of ‘blue 
clay botton” (presumably of the Port Hudson age), into the deep water 
of the Gulf; which point is now nine miles out from the mouth. 
Professor W. C. Kerr read a paper on **A Point in Dynamical Geol- 
ogy.” This paper called attention to the agency of the sun as a probable 
and sufficient explanation of the well-known remarkable coincidences or 
the coast lines, mountain systems and chains of islands, — nearly all the 
great ** feature-lines" in the physiognomy of the globe,—with the arcs of 
great circles tangent to the polar circles; the exceptions being generally 
arcs of great circles perpendicular to the former; inasmuch as the sun os- 
globe in its plastic and formative state. Similar considerations are appli- 
cable to the lunar influence, wbich was cumulative in the same direction. 
THE ONEONTO AND MONTROSE SANDSTONE, ETC. — In the Report of my 
paper on the Oneonto and Montrose Sandstone etc., the language may 
convey the idea that the sandstones of both these localiies have been 
identified with the Portage Group, which was not intended. The Oneonto 
Sandstone is pretty clearly an equivalent of the Portage Group of Central 
