1864. | Geology and Paleontology. 325 
requires to lose twice as much heat as granite in order to cool through 
the same number of degrees. But in regard to the escape of radiant- 
heat through moist air, there is a high degree of difference between them, 
Tt seems that radiant heat will not pass from a given substance through 
the vapour of that substance so rapidly as it will through dry air or a 
vaporous medium of any other substance; and just as the vapour of 
sodium cuts off the light rays of sodium in the spectrum, so the vapour 
of water seemingly, to a great extent at least, arrests the radiant-heat 
rays emanating from water ; and thus, while there is free radiation from 
the snow-capped mountains into the dry regions of the upper air, the 
radiation of heat from the sea is blocked by the “ blanket” of aqueous 
vapour which rests over its surface. Whilst then the ocean in the Glacial 
era retained a temperature considerably higher than at present, Dr. 
Frankland considers the mountains or ice-bearers had undergone con- 
siderably greater refrigeration ; and thus whilst the evaporation of the 
ocean, receiving heat through its earth-floor from the internal molten 
core of our planet, was in much greater volume than now, the moun- 
tains were not very different from their present state, and were efficient 
ice-bearers for the vapours condensed in the upper atmosphere, and 
falling upon them as snow, which, accumulating in vast quantities, 
would not only reduce the level of the perpetual snow-line, but refri- 
gerate also climatal conditions. Not content with this earth alone, 
Professor Frankland attempted, though not very successfully, to apply 
his Glacial hypotheses to the moon, seeking there for traces of glacial 
action. Assuming the solid mass of the moon to have contracted in 
cooling at the same rate as granite, its refrigeration, though only 180° 
Fahr., would, he calculates, create a cellular space within its crust of 
upwards of 14 millions of cubic miles, or more than sufficient to engulf 
the whole of the lunar oceans, if any proportionate to the seas of our 
own earth ever existed there. His final conclusions are, that a liquid 
aqueous ocean can only exist on a planet so long as the latter retains a 
high internal temperature, and that the moon becomes in this respect 
a prophetic picture of the ultimate fate of our earth, “ when, deprived 
of external seas and all but an annual rotation on its axis, it shall 
revolve round the sun an arid and a lifeless wilderness.” The hypo- 
thesis is clever, and contains germs of philosophy and truth, but we 
doubt if geologists generally will accept it, at least in its totality. 
Although the internal-heat and gradually-cooling doctrines are pretty 
generally accepted as theories, and not as still unproven hypotheses, 
these topics, with the Glacial period and the causes of earthquakes, 
still seem productive of a kind of geological nightmare, which dis- 
turbs and terrifies not a few reflective intellects. The Rev. Professor 
Haughton has introduced some of them into an able paper before the 
Geological Society of Dublin— “ An attempt to calculate the Duration 
of Time involved in Geological Epochs.” Commenting on the vague- 
ness of idea involved in the ‘long periods of time” habitually spoken 
of, he undertook, as a point of interest, to estimate, upon the basis of 
a gradual cooling down of our globe, for how long a time it has been 
possible for animals to have existed on it. For this estimate the 
basis selected was Helmholtz’s deduction from the experiments on the 
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