134 REPORT—1846. 
Szcrion I. 
Definition and Phenomena of an Atmospheric Wave. ’ 
When a number of barometric observations are projected on paper accord- 
ing to a suitable scale, and continued for months and years, the eye on 
contemplating them will recognize a variety of curved forms, some of large 
and some of small amplitude; some rising to a considerable altitude, others 
sinking far below the level, representing the mean barometric pressure at the 
station of observation. At first there appears but little regularity in these 
curvilinear records of the ever-shifting state of our atmosphere, but here and 
there the attentive observer will notice some similarity existing between two 
or more individual curves, and he may notice some which possess a certain 
symmetrical arrangement of the ascents and descents. In consequence of 
this similarity and symmetrical arrangement, he examines more carefully the 
records of barometric pressure, and not only discusses the observations at 
one station, but compares those observations with others made at various 
stations ; and here again he finds apparent irregularity and confusion. The 
curves to a certain extent agree, but in many minor points they differ often 
very considerably, in some cases rising at one station while falling at another ; 
this induces a still more minute and careful investigation : the distribution of 
pressure over the largest area he can command is carefully examined ; and 
whether his stations are few or many at any given time, he finds on this area 
a point of maximum pressure and a point of minimum pressure; between 
these points he finds various pressures, generally increasing from the point of 
least pressure to the point of greatest pressure. On some occasions he finds 
a line of high pressure, stretching quite across the area, and on others a line of 
low pressure. By continuing his inquiries for successive epochs, he finds 
these lines of high and low pressure move across the area, or in other words, 
the high pressure or low pressure is gradually transferred from one point to 
another. He also finds at still more remote epochs other lines of high and 
low pressure, some having the same direction with the lines originally noticed, 
and others crossing the direction of the original lines at various angles. 
The questions which now suggest themselves are the following. What 
are these movements? How can they be represented? In what manner 
can they be explained? A simple consideration of the curves suggests the 
idea of waves as explanatory of the phenomena, and the term atmospheric 
wave has been used to designate that ideal individuality which the mind 
attributes to the process which it observes of the successive change of place 
which the barometric maxima and minima undergo, and by which they re- 
gularly succeed each other over the area under examination; this ideal in- 
dividuality has been employed as a mean of examining the movements just 
alluded to. The line of high pressure stretching across the area (the figure 
being supposed to cut this line transversely) has been termed the erest, W ; 
the line of low pressure in advance of the crest, the anterior trough, a (the 
origin of Mr. Scott Russell’s water wave) ; the line of low pressure succeeding 
x >—> xe Fig. 1. 
w 
7 
1 
1 
1 
i 
H 
! 
1 
1 
4 
‘ 
ke 
W, The crest. wa, The amplitude. a, The origin *, 
W a, The front. W h, The height. w, The end. 
W w, The back. 
* Mr. Scott Russell designates the point a the origin; a better term I apprehend would be 
commencement. 
