in @ Voyage across the Atlantic. 129 
to :—About 50 leagues west of the Azore islands, with a south- 
east breeze, dry air and clear zenith, a fog-bank rose in the fore- 
noon from the whole western horizon, and spreading into an 
expanse of clouds continued to advance across the wind (W. to 
E.) until the sky became entirely overcast, and remained so dur- 
ing the rest of the day, with no change in the hygrometric state 
of the air, until a shift of wind to S, and S.W. took place in the 
evening. Then, and not earlier, the hygrometer varied from 
5° (.20) of dryness to 4° and 3°; and next morning, the south- 
west breeze yet continuing, the air appeared nearly saturated 
with moisture, for the hygrometer showed but half a degree, 
(or 2 centesimals) of dryness. After two days, the south-west 
wind gave place to acold northern gale, which partook its 
humidity; and like it was nearly saturated with moisture; but 
gradually recovered dryness of air under a very cloudy aky 
and notwithstanding frequent squalls. 
This and similar instances, afford countenance to the notion, 
that there are ascending currents of damp air, which at one time 
sweep the surface of the sea, and at another, rise into upper 
currents of air, giving place to wind from a different quarter 
beneath. 
Hence they are uncertain and changeable. Not unfrequently 
they veer to an eastern point; and still oftener, the western 
winds take a southerly inclination in the southern hemisphere, 
and northerly in the northern: or are succeeded by winds from 
those quarters, bleak and dry. 
It has been not altogether without surprise, that I have found 
usually considerable dryness of the atmosphere amidst rain. 
In making an observation during a shower, precaution is neces- 
sary to guard against illusion: if the hygrometer be exposed 
to the wet, it of course exhibits the temperature of the dropping 
rain itself, whatever be that of the air; if screened from wet, 
care is requisite to ensure free access of air to the instrument. 
Attending to these points, I still have found 1° or almost 2° of 
dryness (3 to 5 centesimals) in the atmosphere, while rain has 
showered through it. 
Small rain, such as that which accompanies squalls not un- 
