ere, and that the
upper or counter-trade here decends and becomes a surface wind from the S.
W., as the N. E. trade is a surface wind; and that an upper current from
the poles approaches and descends at the same node, to make the N. E.
trade. But it is evident he adopted that conclusion too hastily, as he
obviously did the conclusion that the calms of the horse latitudes were a
type of all. We have seen that the latter are increased by a diversion of
the counter-trade, and that they are avoided by making easting. So it may
be observed that our upper current is a S. W. current, and no northerly
upper current is visible, or exists over the country, however it may be in
western Europe and the North Pacific, on the west of the magnetic poles,
where cold, dry northerly and north-easterly winds are found. The origin
and progress of storms withal demonstrates that no such node can exist.

Two points have been made in relation to the course of the counter-trade
in the tropics, and are relied upon to show its progress there to the N.
E., which deserve consideration.

In the first place, it is well known that "rain dust" falls in
considerable quantities on the western coast of Africa, particularly about
the Cape de Verde Islands, and also upon the Mediterranean and
south-western Europe, where it is termed "sirocco dust."

"This dust," says Lieutenant Maury, "when subjected to microscopic
examination, is found to consist of infusoria and organisms, whose
_habitat_ (place of abode) is not Africa, but South America, and in
the S. E. trade-wind region of South America. Professor Ehrenberg has
examined specimens of sea dust, from the Cape de Verdes and the
regions thereabout, from Malta, Genoa, Lyons, and the Tyrol, and he
has found such a similarity among them as would not have been more
striking had these specimens been all taken from the same pile.

"South American forms he recognizes in all of them; indeed, they are
the prevailing form in every specimen he has examined.

"It may, I think, be now regarded as an established fact, that there
is a perpetual upper current of air from South America to north
Africa, and that the volume of air in these upper currents, which
flows to the northward, is nearly equal to the volume which flows to
the southward with the N. E. trade-winds, there can be no doubt,"
etc.

Now, it is doubtless true that this dust is