from a distance to supply their void. Hourly observations,
with especial reference to this and the following head of inquiry,
should also be made off the western coast of Africa during the
homeward-bound voyage.

Immediately connected with this part of the outward-bound voyage, hourly
observations, as often as circumstances will permit, while the ships are
sailing from the Madeiras to the equator, will be extremely valuable in
elucidating the origin of the great system of south-westerly atmospheric
waves that traverse Europe, and in furnishing data for comparison with
the amount of oscillation and other barometric phaenomena in the Gulf of
Mexico and the Caribbean Sea, a portion of the torrid zone essentially
different in its configuration and in the relations of its area to land
and water, as contra-distinguished to the northern portion of the
African continent; and these hourly observations are the more desirable
as the vessels may approach the land. They may be discontinued on
passing the equator, and the three-hourly series resumed.

There are two points in the southern hemisphere, between 80 deg. west
longitude and 30 deg. east longitude, that claim particular attention in a
barometric point of view, viz., Cape Horn and the Cape of Good Hope; the
latter is within the area marked out for the three-hourly observations,
and too much attention cannot be paid to the indications of the
barometer as vessels are approaching or leaving the Cape. The northern
part of the South Atlantic Ocean has been termed the _true Pacific Ocean
of the world_; and at St. Helena a gale was scarcely ever known; it is
also said to be entirely free from actual storms (Col. Reid's 'Law of
Storms,' 1st edition, p. 415). It may therefore be expected that the
barometer will present in this locality but a small oscillation, and
ships in sailing from St. Helena to the Cape will do well to ascertain,
by means of the three-hourly observations, the increase of oscillation
as they approach the Cape. The same thing will hold good with regard to
Cape Horn: it appears from previous observation that a permanent
barometric depression exists in this locality, most probably in some way
connected with the immense depression noticed by Captain Sir James Clark
Ross, towards the Antarctic Circle. The general character of the
atmosphere off Cape Horn is also extremely different from its character
at St. Helena. It would therefore be well for vessels sailing into th