48 REPORT—1848. 
in connection with those enumerated in former reports, our attention is 
arrested by the distinctness with which the waves Nos. 1 and 2 are exhibited, 
and the striking individuality appertaining to the wave a, determined in the — 
first instance by only two sets of observations, those at Alten and Lougan, 
from the opposition of their barometric curves, and afterwards fully confirmed 
by the observations at St. Petersburgh. ‘I'he facility with which we are 
enabled to trace, during the nine days of examination, the progression of the 
area of greatest pressure, which results from the presence of the crests of 
these waves, and the modification of form which this area of greatest pressure 
undergoes from the different positions of waves a and No. 2, and also from 
the different direction as well as position of wave No. 1, such modification of 
form not being at all recognizable as the effect of any single movement, but 
clearly resulting from such movements as have by this discussion been 
brought to light, leads to the conviction that during the first nine days of 
November 1842, the waves having reference to that period, which are par- 
ticularized in Table VII., were the only atmospheric waves of considerable 
magnitude that during those days flowed over Europe. We are therefore 
enabled to specify, as prominent results of this inquiry, two large waves, 
one about double the breadth of the other, coming over from the north-west, 
the largest extending indefinitely—so far as we can learn from the observa- 
tions before us—towards the north-east, from a line passing between the 
Orkneys and Christiania towards the south-east, and covering first with its 
anterior, and afterwards with its posterior slope the whole of Northern 
Europe. The smallest wave is traced to a much greater extent longitudi- — 
nally, Cork and Alten being the extreme stations indicating the presence of 
its crest: its posterior trough appears to have been contemporaneous and H 
continuous with that of the largest wave; so that while the crest of the — 
largest wave traversed Eastern Europe, the crest of the smallest crossed 
Central Europe, the trough common to both passing over the British Islands 
at the same epoch. We are also able, in addition to these waves, to parti- 
cularize another, having a different direction, its crest extending N.W. toS.E. 
from Ireland to Switzerland; so that in the course of its progress to the 
north-east it crosses them : the half breadth of this south-westerly wave, as 
manifested by its anterior slope, extended from Geneva to or beyond St. — 
Petersburgh. The posterior slope gave a somewhat similar result. I 
While we are able to indicate the amplitude, altitude, direction, march, ze 
and velocity of the atmospheric waves above specified, our knowledge is — 
greatly deficient relative to their longitudinal extent; nor are we able to — 
exhibit on a chart, at any given moment, the line of crest and the bounding — 
troughs of any one of these waves so as to exhibit to the eye the extent of 
surface it covers in the totality of its existence. ‘That these blanks can be © 
filled with less difficulty than might at first sight be imagined, is evident i 
from the ease with which it is possible to determine the elements of a wave 
from two sets of barometric observations, each at a different station, provided 
such observations present opposite movements. In the case of the south- — 
westerly wave above specified, we have only to find a point as much to the — 
south-west of Geneva as that city is south-west of St. Petersburgh, and we ~ 
shall again have opposite movements to those at Geneva, provided the locality — 
of genesis of the south-westerly waves is situated still further to the south-_ 
west, and that the movements do not receive considerable modification from — 
the influence of the north-westerly waves. The distance between the two 
extreme points of opposite movements, as referred to the central point, will 
mark the amplitude of the wave, and these points will be situated in the — 
