C 557 ] 
I, who am one of no great Obfervation, have fre- 
quently feen different Currents in the Air, at the 
fame Time, and in the fame Quarter, under one 
another. For Example: When the under Current 
has been Eaft, the upper Current has been South- 
weft, and the middle South-eaft. I fhall appear 
ridiculous, if I fay I fee the Wind; the Vulgar think, 
that Swine only are endowed with that Quicknefs of 
Sight. Ido not fay, that I can fee the Wind ; but I 
have often feen Clouds, Weather-cocks, Smoke, and 
fuch-like Things, that are either carried or turned by 
the Wind. Smoke and Vanes are fo near, that they 
can hardly caufe any Deception ; fome Clouds may, 
unlefs properly obferved: For when there arc Two 
Tire of Clouds, both carried the fame Way, and with 
the fame Velocity, the upper Tire fhall appear to 
move diredly contrary to the lower ; which Decep- 
tion is owing to the different Angles that Objeds of 
the fame Magnitude, at different Diftances, make on 
the Retina. 
The way to obferve the Motion of the Clouds, is 
by looking at them and a fixed Objed at the fame 
time, as the Sun and Stars, fometimes: The beft 
fuperior fixed Objed is the Moon in her Quarters, 
which may be then feen by Day-light, without offend- 
ing the Eye. The fixed Objeds below the Clouds 
are, a Ridge of Hills, lofty Buildings, or, for want of 
them, a Tree. By obferving a Cloud with any fixed 
Objed, you will not only fee on what Point of the 
Compafs the Clouds pafs ; but you will fee alfo the 
Motion of the upper and under Current: By this 
means you will find, as the Cafe happens, either both 
Currents going the fame Way, though with different 
Z z z ap- 
