ON THE VERTICAL MOVEMENTS OF THE ATMOSPHERE. 169 
which carries the registering paper can be detached by loosening a clamping- 
screw which fastens it to the support turned by the clock, so that the sheets 
can be removed and replaced with speed and facility. 
The entire apparatus was constructed by Mr. Spencer, of Aungier Street, 
Dublin; and he has executed the portion connected with the indication of 
horizontal moyement in such away, that the addition of a registering apparatus 
for this part of the instrument will not only be easy, but will render the 
entire combination a complete indicator of the absolute direction of the wind. 
The results of the instrument in its present state are exhibited on the regis- 
tering sheets as nearly vertical pencil lines, some above and some below the 
neutral line, to which each sheet is carefully adjusted. 
The anemoscope is at present so placed as not to be overtopped by any 
building ; for it stands on the roof of one of the highest houses in Dublin, in a 
quarter remarkably open, and close to the south suburbs. 
Owing to a variety of delays and obstacles in finishing the apparatus, it was 
not brought into action until the 31st of August, and thus I am able to report 
only on the results furnished by little more than the records of a single month. 
These records appear to indicate that vertical oscillations prevail more during 
the mid-day hours than at other periods; for although ten sheets show no 
definite predominance at any specific period of the day, and two predominance 
of vertical movements towards midnight, twenty-one show that these move- 
ments are most frequent at the hours about noon. From a journal of the 
weather which was kept at the same time, it appeared that on bright days, 
when the air had little horizontal motion, gentle upward movements pre- 
vailed at mid-day. Such phenomena are distinctly manifested by the sheets 
for September the 5th, 6th, 7th, 8th, and 9th, and all of these were bright 
sunny days. Before the 5th, the weather had been changeable and unsettled: 
but on comparing the two sheets comprehending from noon of the 3rd to noon 
of the 5th, I noticed that the amplitude of the oscillations of the anemoscope 
progressively and regularly diminished; and it occurred to me that this 
might indicate a tendency towards convective equilibrium of the atmosphere, 
and more settled weather. The weather continued fine until the 13th, when 
there was both high wind and rain, accompanied and preceded by energetic 
oscillations of the anemoscope. If the general circulation of the atmosphere 
takes place, as seems to be now completely established, by a twofold motion, 
one of translation, whether cyclonic or lineal, and the other undulatory, it 
follows that the pulsations of the latter movement may be influenced by aérial 
disturbances. The frequency, regularity, intensity, prevalent direction, and 
more or less intermittent character of these pulsations must depend on varia- 
tions of pressure, density, moisture, and temperature, as well as on the 
rippling motion of the air. It is natural, therefore, to expect, what our 
limited number of observations seem already to indicate, namely, that the 
sudden and abrupt commencement of such pulsations is usually a precursor 
_of other disturbances, while their gradual and regular diminution in energy 
would show a tendency in the air to approach a state of convective equili- 
brium, and might, therefore, be safely relied upon as a forerunner of fine 
weather. This point is illustrated by the remarks of the late Professor 
Daniell relative to the rapid oscillations of the water-barometer during high 
winds, and their gradual diminution preceding a return to a calmer state of 
the air*, Although the atmospheric pulse is undoubtedly compounded of the 
-undulatory movements resulting from the flow of an elastic fluid over the 
* Phil. Trans. 1832, p. 573. 
