ON ATMOSPHERIC WAVES. 
.371 
The barometric curve at any one station being acompouml effect resulting 
from the transit of two or more individual atmospheric waves, before we shall 
be able fully to explain the symmetrical curves, as they occur year after year 
in the southern and south-eastern parts of our island, as well as the decrease 
of oscillation especially from the north-west towards the nodal point, Brussels, 
and assign the numerical expression of its incruase iu different directions from 
this nodal point, it will be necessary to study the individual waves, and en¬ 
deavour clearly to apprehend them in the totality of Uicir e.\istence ; until we 
can do this we shall be unable to assign the true causes of the symmetrical 
curve. To assist iti this part of the inquiry, we have already alluded to tlie 
importance of extending the range of observation, both in a northerly and 
southerly direction, but especially towards the 9outli-we«>t : observations from 
the Mediterranean, as suggested by Sir John Ilerschel, will also be extremely 
important. 
A most important point appears to be developing itself by means of such 
observations os form the subject of the pniscnt mport: tw'o localities of 
great interest arc brouglit prominently into view. The observations from 
Uie north-west appear most strongly to indicate that, somewhere in that di- 
ri'ctioij, the origin of the great barometric disiurlmnces, a centre of oscilla¬ 
tion giving rise to the waves tliut puss onwards towards the south-east, is to 
be sought Wc have already mentioned Iceland as an important station, 
and under the aspect just contemplated its importance is considerably in¬ 
creased ; its proximity to tlie coast of (ireenlaiid will render it still more valu¬ 
able as a connecting link between tliu great Auu'ricao and European systems 
of waves. From tiia point of disturbance, whenwer situated, the greatest 
decrease of oscillation U noticed towards the south-i-ast, or, more strictly 
speaking, on a line from the Orkneys to Brussels; this line more or less ranges 
along the eastern coasts of Scotland and England, aud conducts us to the 
locality of least oscillation, the nodal point Brussels, already noticed. Were it 
not fur the south-westerly system of waves, which art* continually crossing 
those from the north-west, the numbers representing the decrease of oscilla¬ 
tion from the Orkneys to Hnissols couhl readily be ascertained; but before 
we can do this in a satisfactory manner we must be well-acquainted with the 
phienomeiia presented by the south-westerly system, and especially aseer-. 
tain if this set of waves also exhibits a decrease of oscillation with its amount, 
should it do so. Under this aspect, observations from the south-west will 
possess a much greater value, than by considering them only as important to 
determine the longitudinal directions of the crests of the uorth-west waves. 
Of the grant of £10 placed at my disposal, I have expended £6 9s. 3d. 
In order to carry on tlie investigation, especially with regard to the Russian 
observations, I most respectfully solicit a continuance of the grant. 
W. R. Birt. 
EvpI^ANATION of P1-AT88. 
Plate 1. Consists of a selection of twenty curves, that are so arranged as to 
exhibit the modillcatiuns of form, decrease of oscillation aud ap¬ 
proach to symmetry which are observable as we proceed from the 
north-west, the locality 0 ^ greatest barometric disturbance, towards 
Brussels, the itodal jmint of the two principal European systems of 
atmospheric waves. In the first five curves, which are from stations 
bordering on the Atlantic, and embracing nearly the whole of the 
north-western boundary of the British Isles, the greater amount of 
oscillation is well seen. The decrease of oscillation, the change of 
form, and the approach to symmetry, become apparent in the Scotch 
curves, as wc recede IVom the area of greatest disturbance; and 
2 n 2 
