62 REPORT—1843. 
travelling westwards, but the direction of its length, and therefore that of 
its advance, remaining undetermined for want of other stations, its velocity 
must also remain so, only that it must have equalled or exceeded 125 miles 
per hour. 
The effect of diurnal oscillation is evident in both these curves, but most 
so in the London one, by a relative minimum occurring at 4 P.M., and a rela- 
tive maximum at 10 P.M. The morning minimum is also perceptible enough 
in the London curve, but the corresponding maximum cannot be traced in 
either. 
September 1835.—Markree, London and Greenwich, Brussels, Geneva. 
Diurnal oscillation.—In all the curves the afternoon and nightly minimum 
and maximum are perfectly distinct, and indeed finely developed. The morn- 
ing and forenoon ones less so, except in the Geneva curve, where the fore- 
noon maximum is very evident. 
When these are abstracted and slight irregularities rounded off, the London 
and Greenwich curves exhibit a very steady fall during the whole series, 
amounting to 0°38 in. in twenty-six hours, and being perceptibly accelerated 
towards the end of the series. The same holds good for Brussels and Geneva, 
but at these stations the total fall is much less, viz. 0:11 in. for Brussels, and 
0:07 in. for Geneva. On the other hand, at Markree, the descent, which from 
noon till midnight of the 21st had been gentle (amounting to 0:08 in.), begins 
then to accelerate, and terminates the curve with a bold and decided down- 
ward sweep, traversing no less than 0°59 in. in the subsequent thirteen hours. 
On referring to the observations of wind and weather on this occasion, this 
fall of the barometer appears to have been the precursor of a pretty stiff gale, 
which was also felt in London, from the south-west. 
December 1835.—Markree, London, Brussels, Geneva, Gibraltar. 
Diurnal oscillation —Very conspicuous in every one of the curves, both the 
maxima and minima being unequivocally and strongly marked. When the 
effect of these is allowed for and abstracted, all the stations exhibit a steady, 
uniform, and (with exception of Markree, where it was somewhat slower) an 
equally rapid rise in the barometer during the whole extent of the projected 
series. Considering the season of the year and the extent of surface embraced, 
this must be allowed to be not a little remarkable. To take in an effect of 
this nature, we must enlarge our conception of an atmospheric wave till it 
approaches in some degree, in the extent of its sweep, and the majestic regu- 
larity of its progress, to those of the tide-waves in the ocean. The total ele- 
vation or barometric height of the portion of this wave within the limits of 
observation, amounted to about 0°22 in. on an average of the several stations, 
exclusive of Markree, where it did not exceed 0°16. 
March 1836.—Markree, Limerick, Blackheath, Greenwich, London, Brus- 
sels, Maestricht, Geneva, Cadiz, Gibraltar, Tangier. 
The effects of the regular diurnal oscillation are very distinct throughout 
the series for London and its environs, Brussels and Maestricht. The fore- 
noon maximum on the 22nd is also very conspicuous at Geneva, but the 
morning minimum there is marked in its influence on the course of the curve 
by a very curious feature, of which more presently. In Markree, Limerick, 
and the south European stations, the diurnal oscillations are not traceable, 
or but indistinctly. Abstraction made of these oscillations, the English and 
Belgian curves agree in indicating a downward movement throughout the 
series, at the rate (nearly uniform) of about 0°14 in twenty-four hours. In 
this movement Geneva also agrees, with exception of one interruption arising 
from the singular feature above alluded to. But the Irish curves separate 
themselyes in the most decided manner from this law of progress, and ap- 


