J. D. Dana—The overflows of the flooded Connecticut. 497 
Finally, then, it appears that though we are justified, on 
grounds established by Helmholtz and Ericsson, in believing 
in the constancy of the heat-supply within the solar envelope 
for periods to come which are with reference to our terrestrial 
past almost infinite, we are not justified by our present investi- 
gations in asserting that the solar radiation has been constant 
during geologic periods, or is certain, or even likely to remain, 
what we now see it during corresponding periods in the future. 
If there be great cyclical changes of long period (and in our 
present ignorance we can only say that such are not antecedently 
improbable) there will be corresponding changes in terrestrial 
temperature; and it is allowable to inquire whether we do not 
find here matter for consideration in connection with those 
great changes of temperature in past epochs which have in 
them nothing hypothetical, which geology assures us have in- 
deed existed, and for whose possible cause no satisfactory sug- 
gestion has hitherto been made. 
Art. LX.—On Southern New England during the melting of the 
Great Glacier.—Supplement: The Overflows of the flooded Con- 
necticut ; by JAMES D. DANA. 
Ww e 356 of this volume, I have 
Stated that the reindeers must fare been living in the Quinni- 
onnecticut. It is evident that such overflows would have had 
an important influence on the geology of Southern New Eng- 
nd, and I therefore present here the evidence I have been 
able to collect with regard to their positions and courses. 
I. Tur Connecricur VaLLEY BEFORE THE GtactaL Froop. 
It is well known that, in the Triassic period, and probably 
also the J urassic, the Connecticut valley, from New Haven to 
Northern Massachusetts, was occupied by a brackish-water es- 
tuary—its length over 110 miles, its width for the most of the 
Way 20 miles or more. Farther north, the ont for a long dis- 
tance is narrow, and here the waters were probably those of a true 
