Review of Recent Geological Literature. 4<>1 
difficult, in the southern states, to draw a definite plane for the l>a6e of 
the Pleistocene or Quaternary deposits. 
Eocene limestone strata, referable to the Vicksburg or highest divis- 
ion of that series, are known to have a thickness of 1,066 feet, from 212 
to 1,278 feet, in a boring at St. Augustine, at which depth the bottom 
was not reached; but the combined maximum thicknesses of the Neo- 
cene formations of Florida are probably somewhat less than 1,000 feet, 
of which about one half consists of the Jacksonville limestone and as- 
sociated beds. Over most of the peninsula the Neocene is estimated 
not to exceed 250 feet, and in many places to be less than 100 feet. 
Above the bed rocks two conspicuous sand, formations cover the 
greater part of Florida. The lower is a very tine-grained, yellowish, 
clayey sand, sometimes 50 feet thick; and the upper is a snowy white, 
more gritty sand, seldom exceeding a few feet in depth. The yellow 
sand forms the main mass of the abundant low sand hills and ridges of 
the central and southern lake district, having contours, as Prof. Shaler 
has remarked, like the kames of New England. This deposit, accord- 
ing to Dr. Dall, is the residuary product from the decay and subaerial 
erosion of the soft Tertiary limestones. The white sand he thinks 
attributable to marine transportation from the coastal region north of 
Florida during some part of the Pleistocene period, when the state sank 
beneath the 6ea level; but apparently it may instead be an extreme re 
suit from subaerial leaching and bleaching of the underlying residuary 
sand, the area not having been submerged at any time in this period. 
T)r. Dall decides from his study of Florida that it had no great 
changes of level during late Tertiary and Quaternary times, while the 
Antillean region and the Atlantic coast northward, probably with nearly 
all of North America, have experienced important epeirogenic move 
ments of uplift and subsidence, which at the north have been supposed 
to account for the accumulation and departure of the land-ice of the 
Olacial period. Some important considerations which have been 
brought forward by Prof. Shaler, however, go far toward establishing 
an opposite conclusion for the Floridian peninsula. He states that fresh 
water was obtained in the boring before mentioned, at St. Augustine, 
to a depth of 900 feet, being succeeded below by saline water to the 
bottom, from which he infers an uplift of the land at least somewhat 
more than 900 feet above its present hight, allowing the salt water orig- 
inally enclosed in these marine beds to be drained out, its place being 
taken and since held by fresh water notwithstanding the subsequent 
depression. Shaler also mentions, in "'Nature and Man in America." 
that a powerful spring of freshwater wells up strongly in the sea "a tew 
miles to the south of St. Augustine and three or four miles from the 
coast-line." Subterranean stream courses are thus known to reach far 
beneath the present sea level, and their channelling in the porous lime 
stones must have taken place when the peninsula was considerably ele- 
vated. 
An explanation may thereby be found for the surprising inequality 
of contour of the residuary sand deposits in the lake district of Klor- 
