rshes, others with sand. All these may be disturbing causes--so are
lofty mountains. From these causes, and the more powerful effect of the
sun's rays in one place than in another, hurricanes and typhoons occur,
and the monsoons are made to blow--the harmattan on the west coast of
Africa; the simoon, with its deadly breath, in Arabia; the oppressive
sirocco in the Mediterranean. What I have said will explain that
beautiful passage in Ecclesiastes, 1st chapter, 6th verse, which shows
the exactness of the sacred writers whenever they do introduce
scientific subjects: `The wind goeth toward the south, and turneth about
unto the north; it whirleth about continually, and the wind returneth
again according to his circuits.' Who gave Solomon this information? I
doubt if any of his sages possessed that scientific knowledge which has
only been attained by philosophers of late years. Perhaps I may still
more clearly explain to you the cause of the circulation of the
atmosphere. I told you that there were two agents at work--diurnal
motion, and the heat of the sun; but to these may be added the cold of
the poles, which contracts the air. Suppose the globe at rest, and
covered with one uniform stagnant mass of atmosphere; suddenly heat,
cold, and the diurnal motion commence their operations. The air about
the equator would expand, that about the poles contract. Thus two
systems of winds would commence to blow--one above, from the equator
towards the poles; and as thus a vacuum would be left below, a current
would come from the poles to supply its place. The diurnal motion
prevents these currents running in straight lines. That coming from the
poles will appear to have easting in them, and those going towards the
poles westing. Not only, however, is the level of the atmosphere
changed by the heating rays of the sun, but its specific gravity. Thus
the heated current moves more easily and rapidly than the colder; and
the latter, consequently, turns back a portion of what was going towards
the poles, and adjusts the equilibrium of the atmosphere. I have
already shown you the great importance of the circulation of the air in
the economy of nature; and how, among the many offices of the
atmosphere, it distributes moisture over the surface of the earth,
making the barren places fruitful, and tempering the climates of
different latitudes, fitting them as the abode of civilised man. But I
will not pursue the subject further ju