ON THE VERTICAL MOVEMENTS OF THE ATMOSPHERE. 167 
Among the phenomena attending the more tranquil conditions of the air, 
I had noticed in my earlier observations, during the summer of 1857, that 
upward currents generally prevailed by day, while downward currents became 
more prominent at night. This alternation was manifestly connected, as 
shown by the horizontal vane, with the action of land and sea breezes ; for at 
this time the observations were made at a point situated about two miles 
from the sea-shore. By day, the convection due to the heating of the lower 
stratum of air in contact with the ground could not take place by equal 
upward and downward exchanges of masses of air, because the place of the 
ascending warm air was partly supplied by the lateral influx of colder sea air, 
which, in its turn, would become sufficiently heated to ascend and give place 
to a fresh lateral influx. By night, the colder air from the land flowed 
towards the sea, and its place was filled by descending currents from above. 
At the same time the warmer air from the sea probably tended to occupy the 
place of these currents, and thus to equalize the temperature of the upper 
and lower strata of air so as to lessen the energy of the convective movement 
over the land. 
Before the termination of the Meeting of the Association at Manchester, I 
had resolved, with the concurrence of Mr. Glaisher, the only other member of 
the Committee then present, to cause a registering instrument to be con- 
structed which would record the existence of non-horizontal atmospheric 
motions. The following is a description of the anemoscope which I ultimately 
decided upon as most suitable in its construction for the purposes we have in 
view. Fig. 1 is a vertical section of the portion of the apparatus which is 
exposed to the wind, and fig. 3 an elevation of the same portion. Aisa 
cast-iron pillar which supports a cup, 2, containing frietion-balls made of gun- 
metal; on these a disk, g, rests, and this is firmly attached to a box from 
which an arm projects at one side, and is terminated by the cone, P, which 
acts as a counterpoise for the opposite and working arm of the anemoscope. 
A short arm, n, shown in fig. 3, supports a wheel, d, in one side of which teeth 
are cut; the other side is firmly attached to a hollow light copper box, B, 
which forms the tail. This box is a truncated pyramid, and while its vertical 
sides are exposed to the horizontal action of the wind, its upper and lower 
surfaces are exposed to its vertical action. This tail is balanced by a coun- 
terpoise, 7, which is connected by a bent arm with the axle of the wheel, d. 
The teeth of this wheel catch those of the pinion, e (fig. 1), and this catches in 
the rack, f. The rack is attached to a shaft, c, which descends through the 
hollow supporting pillar and communicates with the registering apparatus. 
In fig. 2 the most essential part of the arrangements for registering the 
indications of the upper part of the instrument are shown. The shaft, c, 
passes through brass guides, and carries a small circular projecting piece, s, 
which catches in a notch made in the bit, v, attached to the pencil-carrier, p. 
This pencil-carrier is capable of upward and downward motions only, and 
the rod to which it is attached passes through guides. The carrier is, more- 
over, supported by an ivory friction-wheel, ¢, which turns when the piece, s, 
revolves beneath it. 
From this brief description, it is apparent that the cone, P, will always indi- 
cate the direction of the wind in azimuth, like ordinary vanes. At the same 
time the vertical component (if any) of the wind will raise or depress the tail, 
B. In the former case it is manifest that the wheel, d, will cause e to turn, so 
as to raise the rack, f, and in the latter case the effect will be to lower the 
rack. It follows, therefore, that the shaft, c, and consequently the pencil- 
carrier which it moyes, must rise or fall according as the vertical motion of 
