OBSERVATIONS ON HIGH CURRENTS. 115 
Similar observations have been made in the south¬ 
ern hemisphere, and with like results, except that the 
higher air moves to the east and the southeast. 
These observations tell us that the surface winds 
do not blow from the poles, nor the upper currents 
toward the poles, as we had supposed. The trade- 
winds, instead of being polar winds, bend westward 
near the equator—that is, they are northeast north of 
the equator and southeast south of it. Now the 
question arises. What gives them this westward tend¬ 
ency near the equator ? 
The earth, with its envelope of air, revolves on its 
axis once every twenty-four hours. This rotation 
whirls the surface at the equator through space at the 
rate of more than a thousand miles per hour, or over 
seventeen miles per minute. North and south of the 
equator this motion is less and less, until it becomes 
nil at the poles. Now, if water is poured on a revolv¬ 
ing grindstone it flows in from the edges toward the 
middle of the stone, heaps up there, and lags behind. 
As the air is mobile, it is easy to see that in the equa¬ 
torial region it might lag behind and thus turn the 
polar winds westward, and that seems to me the chief 
cause for the deflection of the trade-winds. This was 
Professor Hadley’s explanation as far back as 1Y35. 
From extensive observations it has been learned 
that the envelope of air surrounding the globe revolves 
with it, just as the water in the oceans revolves with 
the land. But if this were true, there could be no 
zone of calms at the equator, since there the rotation 
is most rapid. 
