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periods of time. Yet the physicist may trace the links of 
operation of natural phenomena now in progress, yielding a 
force productive of catastrophic action at epochs alternating 
with periods of such uniform action. 
But we must proceed in our search after this primary 
Cause, out of the realm of Geology, and call upon its sister 
sciences to divulge their secrets of workings in Nature, and 
Meteorology, and Mechanical (Natural) Philosophy, come 
amply to our aid. Meteorology discloses — first, that certain 
natural laws must be obeyed in the elevation to high regions 
of the atmosphere, and conveyance therein by currents, of 
vapour, drawn by solar heat from areas of yield ; and — 
secondly, that natural laws must be obeyed in the circum- 
stances of precipitation of this air-borne vapour. These laws 
are that tropical vapours proceed polarly, and are only 
liable to condensation and precipitation by contact with an 
atmosphere cooled to the degree necessary by surrounding 
circvunstances. Hence, it is ascertained by the meteorologist, 
that next to the tropics, the higher latitudes have the largest 
precipitation of condensed cloud vapour in the various forms 
it assumes, and that such precipitation is largely influenced 
by presence of lofty and snow-capped summits, in areas 
between the largest vapor-yielding surfaces, and its ultimate 
destination, or the point within the margin of the circles of 
frigidity wherein the continuance of vapour in an uncon- 
gealed or uncondensed state is practically impossible. Now, 
in the aspect of Nature displayed on the superficies of the 
earth, wo behold a contrast between one quarter and another 
as to area of vaporization, and its reverse, or radiation of 
dry heat from land surfaces, and also as to the occurrence of 
summits inducing precipitation from impinging masses of 
air-borne vapoiir en route for the poles, as abounding in one 
quarter and wholly wanting in another. Delineate a hemis- 
phere, for instance, according to Mercator's projection. Let 
the periphery of the sphere be delineated as having its 
margin in longitudes 170° west of Greenwich and 10 c east. 
Here we have in the west the vast evaporating area of the 
Pacific, with scarce a point of attraction to precipitation 
between the tropics and Behring's Straits ; while on the east 
we have the heat-radiating and non-evaporating surfaces of 
the continents of Europe and Africa, upon portions of 
which there are snow-clad summits inducing precipitation 
either by direct contact with impinging clouds, or by 
imparting the necessary chill to the atmosphere. The 
sequence of this contrast of circumstances, or conditions, 
is the transference of a vast volume of vapour, chiefly 
