A Rejoinder to Critieisiii on Hypothesis. — Spencer. 115 
cur in beds to an elevation of 150 feet or more, as Dr. Dall 
would have seen had he referred to my work on -Cuba (p. 83). 
And these fossils, from a point nearly opposite the end of 
Florida, were determined by Dr. Dall's colleague under his 
own direction. 
The first real objection, and indeed the only one, appears 
in No. 7, and it is a comfort to reply to it in place of warding 
oiT intangible inferences. Dr. Dall says that with an elevation 
of 5000-6000 feet the plateau of Florida would have been fur- 
rowed into canyons, of which none are seen in southern Flor- 
ida. Certainly in the very low peninsula, such do not form a 
feature. An elevation of 2100 feet would connect the islands 
with the continent, and to this amount I shall here confine 
myself. An uplift of even this much would extend the land 
far beyond the boundaries of my critic's limitations. 
With atmospheric action on such a raised plateau, it be- 
comes dissected, with remnants intact, until the features grow 
old when only ridges and valleys are left. I had seen in the Flor- 
idian channel and its tributaries such dissection, with Florida 
one of the remnants of the original plateau. My observations 
of the erosion features of high plateaus, which are not of 
great antiquity, show that above the head of the incising val- 
leys the surface may show no depressions or only shallow 
channels. So also the canyons or deep valleys should be found 
nearer the edge of the continental shelf than the now very low 
plains of southern Florida, to which Dr. Dall seeks to imit 
the evidence. Even here the surface has been levelled over 
by coral reefs or sand accumulations formed since any sculp- 
turing of the Floridian plateau according to my hypothesis. 
This is confirmed by professor N. S. Shaler who finds great 
changes of level as shown by the following quotations : ''The 
coast line exhibits a number of flooded valleys . . . some of 
these channels . . . are now completely filled with sand plains 
, . . evidently of considerable depth. It is tolerably evident 
indeed, that if the recent deposits . . . were removed the sur- 
face of the Cretaceous and Tertiary beds would be found 
deeply scarred by gorge-like valleys."''' 
The above quotation refers to the surface sculpturing, but 
professor Shaler shows in evidence of a great elevation of the 
• Bull. Geol. Soc. Am., vol. vi, p. 154-. 
