750 Marvels of the Universe 
d 
The “ brave westerly winds” of the southern ocean, by their constant blowing, “ pile the water 
in such heaps,” that by the help of these winds and waves the clippers in the old sailing-ship 
days were enabled to attain such speeds as to arouse the wonder of all, though of course such speeds 
are far inferior to those of Atlantic liners nowadays, gained by means of a reckless expenditure 
of coal and at heavy risk to 
human life. 
Summed up in a very few 
words, the general circulation 
of the air is as follows. Over 
the equator there is a zone of 
medium pressure, having on 
either side (lats. 30° N. & S.) a 
belt of higher pressure, within 
which the trade winds blow 
throughout the year, except 
over the north part of the 
Indian Ocean, where in July 
we get the “south-west 
monsoons” and in January 
the “‘north-easterly ’’ winds. 
Further north and south (pole- 
wards) of these regions the 
surface winds in general blow 
polewards, in Europe the 
south-west wind being the most 
prevalent one. The trade wind 
zones shift slightly during the 
course of the year, owing to 
the southward and northward 
motion of the sun. There is 
an upper current blowing from 
the equator polewards, known 
in tropical regions as the “ anti- 
trade,’ at a height of some 
ten thousand feet above the 
surface; but this gradually 
descends till in latitude 40° its 
lower portions are not far from 
the ground. Recent researches 
by means of kites with self- 
Photo by] ' (ZL. J. Wallis. a : 
THE OLD MAN CACTUS. recording instruments have re- 
One of the most singular-looking of the tribe. Some of the specimens present vealed the presence of very 
a close resemblance to a back yiew of an aged man’s head clothed with long rapid currents in the upper alr, 
silvery locks. 
whose directions and_ speeds 
differ much from those observed nearer the surface, and it has been suggested that by taking 
advantage of these swift-moving upper currents (above five thousand feet from the ground) flying 
machines may be able to attain speeds greater than those of an express train ! 
Of the smaller air movements or sound waves many methods are given in works on 
physics whereby these may be rendered visible and measurements as to their length taken. 
