426. Prof. Hennessy on the Vertieal Currents 
The upward currents were decidedly longer in duration than 
at 6 P.M. 
“91 p.w.—Wind still from N.W.; upward currents, with 
alternating currents at intervals of about one minute. 
“July 11.—Wind W. A beautiful day, with a few light clouds 
scattered over the sky. During the afternoon, up to 5 P.M., a 
strong breeze, with very decided upward currents. At short 
intervals the disc oscillated, showing a downward tendency. 
“ July 14.—Before 9 a.m., the wind was E.S.E.; a moderate 
breeze with downward tendency, Light clouds were observed 
to move in a direction opposed to the wind at the earth’s surface. 
10.30 a.m., wind S.E.; an increase of clouds (cumuli) ; both 
vane and disc were oscillating ; downward tendency of currents 
was marked. At 1 o’clock in the afternoon, a fog was seen out 
at sea, which, as it approached the shore, ascended in clouds over 
Howth. 
“ August 6, 10 4.m,—Wind N.E. ; alternate currents, down- 
ward predominating... The sky was covered with light clouds, 
and the temperature comparatively low. 
“ August 20.—An extremely fine and warm day, with a clear 
sky. The air was nearly still; and the dise continued to indicate 
faint and steady upward currents; for the flange continued at an 
upward inclination of a few degrees for long intervals, sometimes 
exceeding one hour. The movements of smoke that could be 
observed at the same time showed a similar tendency. 
“ August 21, 7 a.m.—Wind E.S8.E., with no vertical currents ; 
after 8, the disc began to move, and the flange was some- 
times inclined upwards at a very small angle. It frequently re- 
mained perfectly level, although a very perceptible breeze was 
blowing. After 10 a.m. the upward tendency became more 
manifest, and it generally remained for long intervals inclined 
at an angle of from about 5° to 8°. 
“ August 24, 5 p.m.—Before and during a heavy shower the 
dise exhibited the presence of downward currents. 
“September 3, 8 a.m.—Wind blowing in sudden gusts from 
N.E.; the dise showed vertical currents, chiefly with a downward 
tendency ; rain followed at about half-past nine.” 
5. The few results which were thus recorded seem to show that 
the study of the non-horizontal motions of our atmosphere is 
desirable, not only among mountainous districts, but that it may 
form a portion of our general inquiries under all local cireum- 
stances whatever. It appears that the wind rarely blows parallel 
to the surface of the earth, and that the air, while in rapid motion, 
is always undergoing a process of undulation, whereby the direc- 
tion of the axis of a current at any point above the earth is 
changed alternately, so as to be more or less inclined upwards or . 
