166 REPORT—1862. 
winds as well as storms are almost always conceived as currents flowing in 
perfect parallelism to the earth’s surface. It is true that no physical theory 
of the motions of the atmosphere can be attempted without some considera- 
tions which involve the necessity of vertical and oblique motions among the 
masses of air, as well as horizontal motions; but while direct comparisons of 
the latter among themselves have continued for many years to be made in 
different parts of the world, we possess scarcely any such data relative to 
non-horizontal movements as would enable us to make them subjects of exact 
inquiry. 
ihe only writer who, as far as I am aware, has hitherto endeavoured to 
deduce any well-defined results from observation relative to the vertical 
movements of the atmosphere is M. Fournet, and his studies were almost ex- 
clusively directed to the elucidation of the phenomena of some remarkable 
local winds that frequently prevail among the Alps and in the valley of the 
Rhone*. A local phenomenon in Ireland + induced me to study the vertical 
motions of the air in a more general way than was necessary for the explana- 
tion of this phenomenon itself; and my first step was an attempt at devising 
a vane capable of showing the existence and direction of non-horizontal 
currents. This was a non-registering instrument, and the results obtained 
were therefore somewhat unconnected; but they seemed to establish some 
important relations between vertical currents and other atmospherical dis- 
-turbancest. Among these, I may be permitted to notice the phenomena 
which preceded the disastrous gale of February 9, 1861. For many days, at 
the close of January and beginning of February, the weather was remarkably 
fine, and no vertical currents were observed; but on the 7th very distinct 
evidences of vertical disturbance came under my notice, while the air had as 
yet no remarkable horizontal motion. On the 8th, at 2 p.w., my attention 
was called to the vane by its shifting round through N. towards N.E., with 
decided and frequent downward plunges of the disk exposed to the vertical 
action of the air. It appeared as if showers of cold air were descending ; for 
the thermometer showed at the same time a rapidly falling temperature. 
While vertical convection had become already highly developed, the horizontal 
motion of the air was not as yet greater than that of an ordinary brisk 
breeze. 
Next day, during the storm, although the disk of the vane was in constant 
oscillation from the undulatory motion which my observations had already 
shown to be a necessary accompaniment of all high winds passing over 
terrestrial obstacles, no marked prevalence of upward or downward motions 
could be observed corresponding to the plunges of the disk noticed on the 
preceding day. The mercury in the barometer had been falling with great 
regularity during four days before that on which I had noticed the first 
decided indications of vertical disturbance. On that and the next day, as 
well as on the very day of the storm, the barometric column was rising, 
while the temperature was steadily falling. Here the rise in the barometer 
was accompanied by north-easterly winds, and the air at the earth’s surface 
was thus rapidly mingled with cooler masses descending from above, as shown 
by the vane; so that the increased pressure was due to the increased density 
of the entire aérial column above the barometer. 
_ * See Annales de Chimie et de Physique, tome lxxiy. p. 337; and a réswmé of his results 
in a note to M. Martin’s translation of Kaemtz’s Meteorologie, p. 35. 
+ Proceedings of the Royal Irish Academy, vol. iv. p. 279. 
} Atlantis, vol, iii,” p, 166; Phil. Mag. for May 1860; and Proceedings R. I. A. for 
May 1861, p. 232, 
