ON THE REDUCTION OF METEOROLOGICAL OBSERVATIONS. 63 
pear to have been under the influence of some cross wave, or local cause of 
disturbance not extending to any of the other stations. These curves both 
commence with a falling barometer, but a minimum is attained about 6 P.M. 
of the 25th (6"), after which they rise rapidly, and continue to do so; in the 
case of Markree to the end of the projected series ; in that of Limerick, nearly 
so, a maximum being apparently reached about the 25th hour (1 p.m. of the 
22nd). 
io curves for Cadiz, Gibraltar and Tangier, are all marked (and more 
especially the two latter) with that peculiarity which has already been no- 
ticed in the Geneva curve, and which consists in a sudden and temporary 
elevation and depression, forming a kind of hump or abrupt bulge upwards. 
At Geneva and Gibraltar this occupies the interval from the 11th to the 15th 
hour (11 p.m. tc 34.m.). At Tangier it is two hours earlier, viz. from 9» 
to 13, but in all three cases equally pronounced, and of about the same 
elevation, 0°033 in.; not a very large quantity, it is true, but quite unequivocal, 
and beyond all reasonable limits of error of observation. At Cadiz it also 
oceurs, but less distinct and less abrupt, running into the swell caused by the 
nocturnal maximum of the regular oscillation, as is also in some degree the 
case at Geneva, and of which maximum it is probably some abnormal affec- 
tion, rather depending on the general state of the atmosphere as affecting ra- 
diation (of which I shall have more to say presently), than the effect of any 
wave-like disturbance striking on the stations at the times in question. The 
winds and weather noted at the stations afford no elucidation of this curious 
peculiarity. 
June 1836.—Markree, Limerick, Oxford, London (with Greenwich and 
Blackheath), Brussels, Hanover, Geneva, Turin, Cadiz, Gibraltar. 
This term exhibits a considerable want of accordance between the British 
and continental stations. To begin with the latter. The diurnal oscillations 
are well marked at Brussels, Geneva and Turin, both the minima and both 
maxima being clearly exhibited. When these are abstracted the curves be- 
come nearly level, a slight tendency to descend only remaining for Brussels 
and Geneva, and to ascent for Turin. At Cadiz and Gibraltar also, the 
afternoon minimum and nocturnal maximum are clearly expressed, and being 
eliminated, the curves up to about the 14th hour at Cadiz, and the 17th at 
Gibraltar, assume the flattened and slightly-descending character of those 
belonging to Brussels and Geneva. But at these hours respectively a re- 
markable change comes on which completely masks the oscillatory move- 
ments. In fact, a bulge upwards rather than a depression takes place in the 
Cadiz curve between the 14th and 18th hours, and a sudden abrupt upward 
start (of 0°03 in.) in that of Gibraltar at the 18th, which as it were dislocates 
it, and places all the rest of its course on a higher level. In speculating on 
the origin of these peculiarities, I have been led to consider them as probably 
due to the immense radiation of the African continent, with its cloudless 
skies, chilling and contracting the superincumbent atmosphere, and giving 
rise to a nocturnal influx from all quarters, but chiefly from the adjacent 
ocean. Such an influx, suddenly checked and reversed in its direction by 
the approach of the sun to the eastern horizon, would evidently tend to pro- 
duce phzenomena of the kind. 
The curve for Hanover of this term deviates totally from the type of those 
described, offering a regular and considerable rise and fall, in which the 
effect of the diurnal oscillations is completely merged. The maximum of the 
series occurs at or about 16", the total rise from the lowest point being 
0°22 in., and that of its subsequent depression to what appears to be a mini- 
mum, at the end of the series, of 0°13 in. These features tend to separate 
