54 The Americmi Geologist. January, i899 
th other. Evidence of the temperate age everywhere precedes 
the evidence of the Ice age. In some regions the Ice age yet 
exists, but l)eneath the ice is found evidence which estabHshes 
tlie prior existence of milder cHmates.* 
The Tropical Conditions of the Mesozoic and Palao zoic- 
Ages. During tlie Jurassic ammonites tlourislied well up to 
the polar circles, and how much further geological research 
has not yet been able to determine. It would be useless to 
recite to the youngest students in geology the facts which 
could be massed to prove the universal distribution of the 
tropical flora and fauna of the Mesozoic and Palaeozoic ages.f 
The manuals and textbooks of geology are overburdened 
with illustrations. That an age of tropical climates existed 
prior to the temperate age may be considered a geological fact, 
as it is universally taught in the textbooks of geology. 
Underneath the strata of these ages lie those of the pre- 
vious Cambrian and Laurentian ages, whose structure and 
fossils likewise mark a widespread torrid climate. Beneath 
these in turn are the enormously thick rocks of pre-Cambrian 
and Azoic ages, beyond which lie the ages preceding those 
of geology and reaching into the domain of cosmology. We 
are taught alike in the textbooks of the common schools^J; 
and in the profound treatises of geologists and physicists§ that 
during these ages the Earth "was a melted fiery ball sur- 
rounded by a thick atmosphere of gases and vapors." Of this 
stage of the Earth's climatic development, Sir A. Geikie says: 
"At an early period of the Earth's history, the water now forming 
the ocean, together with the rivers, lakes and snowfields of the land, 
existed as vapor, in which were mingled many other gases and vapors, 
the whole forming a vast atmosphere surrounding the still intensely 
hot globe. ■'•^ 
Stages of Clifnatic Evolution. \^arious stages of climatic 
evolution are apparently represented in the conditions of the 
planets Jupiter, the Earth, and Mars. The former is of great 
size, and is apparently shrouded in dense clouds, and appears 
*Am. Geologist. Vol. XX, pp. 343-4. 
tManual of Geology, Dana, 4th Ed., p. 711 and p. 574. 
JTextbook of Geology, Sir A. Geikie, London, 1882. 
§ Warren's New Physical Geography, p. 11, edited by Dr. Wm. H. 
Brewer of Yale. See also Essays, p. 40, Prof. S. T. Hunt. 
^Textbook of Geology, p. 2>?> (London, 1882). 
