[ ] 
pofe it to be Fad. Bat I defire the Objedor to con- 
fider, that, when he is failing, he is on the Top of 
the Water, and at the Bottom of the Air; he per- 
ceives the Current of Water run very faff at Top, 
but does not know how it runs at the Bottom. It 
is very certain, that there are Under currents in Water : 
In Rivers that ebb and flow, it is perceived every 
Tide ; for the Current will run up after it hath begun 
to ebb. By Experiments that have been made, it 
appears, that in lome Places, where the Current on 
the Surface is very ftrong, the Under-current, running 
quite the contrary Way, fhall be much ftronger, and 
carry away a Boat againft the Force of the upper 
Current. 
And why may there not be contrary Currents in 
the Air ? An Element much more lubtile than Water, 
and therefore capable of being put into a greater 
Variety ofMotions. The Sailor concerns himfelf no 
farther with the Wind, than as it fills his Sails, the 
Height of which can bear but a fmall Proportion 
with that Column of Air I am now fpeaking ofi 
The Land-breezes about Iflands, in the Torrid Zone, 
fhew different Currents in the Air. For, in the 
Night, the Wind fhall blow from the Centre of the 
Ifland, every Way, into the Sea, and even in dired 
Oppolition to the Trade-wind, and yet give no Inter- 
ruption to the Progrefs of it, except juft in that little 
Spot, and for a fmall Height too j which is evident 
from hence, bccaufc in failing to the Wcftward of 
Barbadoes , fuppofe, or 'Jamaica , without the Reach 
of the Land-breeze, you feel no Interruption in the 
Strength of the Trade-wind, by Night as well as by 
Day. 
I, 
