128 Mr. Colebrooke’s Meteorological Observations 
same limits, whence the north-east trade blows towards the’ 
equator, a south-west (or rather west-south-west) wind, not un- 
commonly prevails in the contrary direction. So, in the southern 
Atlantic, from the limits of the south-east ¢rade, the preva- 
lent winds are nearly converse, (west-north-west.) Now, ad- 
verting to these winds blowing contrariwise from the same limit, 
there is difficulty to conceive the origin of either ¢rade, but as 
derived from upper strata of the atmosphere : and, if that source 
of supply at the commencement be acknowledged, there is little 
reason for rejecting it in the wind’s subsequent progress. 
In the trade-wind humidity is gently rising ; and cool air de- 
scends in a slanting direction towards a warmer region: the 
vicinity of the equator. 
In the averse wind, vapour in solution ascends, with warm air, 
which passes towards a colder and more elevated region. 
Both are undulating currents: but, in one, dry air descending 
is characteristic; as, in the other, moist air ascending. 
The western winds that prevail beyond the range of the east- 
erly ¢rade-winds, not blowing with the same constancy, present 
not an equal opportunity for a followed series of observations of 
them within a brief compass. It is apparent, however, that the 
western winds are, in general, more charged with humidity than 
the eastern; and winds, receding from the equator and tropics, 
more so than those which are pointed towards the equator. 
Rising currents of damp air do certainly occur: not merely 
presumed or surmised; but clearly presented to notice, and 
made manifest by clouds drifted with them. 
Upon numerous occasions, when the wind has been in a differ- 
ent quarter, the unconformable course of clouds has distinctly 
shown a superior current loaded with humidity. Several times, 
in both hemispheres, I have particularly remarked clouds moy- 
ing across the wind, drifted evidently by an upper current; for 
example, from west to east over a south-east breeze, in the nor- 
thern hemisphere; and from north to south above an easterly 
wind in the southern. 
To dwell upon the particulars of one instance here alluded 
