vt ON ATMOSPHERIC WAVES. 163 
namely, from N.W. and S.E.; and it has been suggested that these two sets 
of oppositely directed currents, N.E.—S.W. and N.W.—-S.E., continually cross- 
ing each other, occasion the complexity of the barometric and anemometric 
phenomena, and that in future discussions these should be particularly taken 
into account. Should the views thus advanced be substantiated, we are 
beginning to unravel some of the complicated problems of meteorological 
research : still much remains to be done; we are as yet only on the thresh- 
hold of the vast meteorological arena now opening upon us. The subject, over- 
whelming with interest, naturally divides itself into two branches. First, the 
determination of the phases of the larger undulations,—-the barometric curves 
which include complete elevations and depressions of the barometer, and 
which represent, and are exponents of, the effects resulting from contemporane- 
ous transits of waves or systems of waves such as have been previously 
noticed. These, with the smaller secondary waves superposed on their slopes, 
form the types of the various seasons of the year. Second, the absolute extent 
of each normal wave of each system in space, as it exists with the smaller 
superposed waves riding on its slopes. ‘The direction of its crest, its am- 
plitude in miles, the altitude of its crest above, and the depression of its 
troughs below the surface of general repose of the atmosphere, the place of 
its formation, the manner in which it is propagated, the precise direction and 
extent of its motion, the force with which it is translated from place to place, 
and the locality of its final extinction, are questions which the present state 
of our knowledge is inadequate to resolve. 
These desiderata regarding the waves as resulting from parallel and op- 
positely directed currents, may be thus expressed. The absolute extent, both 
as regards length and breadth of each current with that of its counter and 
oppositely directed current, together forming the two slopes of the wave 
with its included trough ; the points or lines of intersection of the two systems 
of parallel and oppositely directed currents; the precise direction of the 
conterminous edges of the currents, the lines in which the velocity of the 
wind is greatest answering to the included trough; the amount of the dimi- 
nution of pressure resulting from this velocity below the mean pressure of 
the atmosphere ; the locality of the formation of these currents; the direction 
in which they advance with a lateral motion; the force with which they are 
translated by means of such lateral motion from place to place, and the 
locality of their final extinction or disappearance. 
With respect to the first branch of inquiry, the phases of the larger un- 
dulations, the seasonal barometric types, but little has yet been done towards 
its accomplishment. ‘There is some hope, as mentioned in the foregoing re- 
marks, that we have obtained the type of fourteen days in November for one 
locality only ; and we have also a glimpse of the character of the movements 
during a portion of October. This is however very small compared with 
the extent of the problem. At the utmost it will only amount to the twelfth 
partof the annual type; even the 24th cannot yet be said to be fully established. 
Again, the station of observation is to be taken into account; were the 
entire year's observations for one station projected, and year after year such 
observations compared, we should only have the annual type at thaé station. 
The examination of the symmetrical wave of 1842 has already shown that 
there is a line of greatest symmetry as far as that wave is concerned, namely 
Dublin, Birmingham, Brussels and Munich; and the discussion of the equi- 
noctial and solstitial observations, 1835 to 1838, has clearly established 
Brussels as a nodal point, and we find it situated on this line of greatest 
symmetry. At very short distances N.E. and S.W. of the line of greatest 
symmetry of 1842, the symmetry is departed from. On the return of the 
great wave in the autumn of 1845, the line of greatest symmetry appears to 
M 2 
