346 REPORT—1846. 
the register paper now ruled for a scale of momentary pressure, we rule 
another scale, that of momentary velocity, or copy the register on a paper 
prepared with such a scale, the ordinates of velocity may be measured off 
with nearly as much accuracy as those of pressure, and the mean velocity 
and total air-movement be approximately obtained with great facility. It is 
obvious that the paper in Mr. Osler’s apparatus may be ruled, as in the speci- 
men, p. 345, both for velocity and pressure, with very little additional expense. 
The pressure lines may be continuous, the velocity lines dotted. Such a 
table shows how imperfectly the registration of wind-pressure to one pound, 
or even one-tenth of a pound per square foot, satisfies the question of the 
velocity of the wind. In many cases winds of several miles an hour have been 
left entirely unnoticed. 
Lind’s Anemometer.—In Lind’s anemometer, the pressure of wind is ba- 
lanced by the weight of a column of water, + the force due to the friction of 
its movement. Owing to the facility of liquid movements, this instrument, if 
made with a siphon of large diameter, is very quick in its indications, and 
prettily exhibits what Mr. Osler’s pencils record, the continual fluctuations 
of the wind. Pressures which move the water to a difference of level of less 
than one-twentieth of an inch, can scarcely be noted accurately, but may he 
estimated to one-fortieth or one-fiftieth. ‘This gives as the limit of wind-ve- 
locity really measurable five or seven miles an hour. 
Lind’s anemometer may be rendered self-registering, but not without 
some sacrifice of its quickness and accuracy *. - 
It is possible to arrange apparatus which shall allow of the flowing of a 
liquid under the pressure of the atmosphere with the velocity due to that 
ressure ; it is also possible so to regulate the direction of this flowing that the 
direction shall be known of the wind to which the efflux is due; and in other 
ways the apparatus may be varied; but it does not appear that by these pro- 
cesses any real advantage can be gained over the instruments of Whewell 
and Osler, when these are properly attended to. I proceed therefore to an- 
other view of the subject. 
Molecular Effects of the Movement of the Atmosphere. 
The class of phenomena to which attention is now requested depends on 
the molecular condition of the air, and on its rate of movement; if it can 
* Table for Lind’s Anemometer. 
Difference The Vel. in 
feelin | renee, | mals Pet 
0°25 13 18-0 
0°5 2°6 25°6 
1:0 iy 36:0 
20 10°4 50°8 
3:0 15°6 62°0 
4:0 20°8 76:0 
50 26:0 80°4 
60 ald 88:0 
7:0 36°5 95°2 
8:0 41:7 101°6 
9:0 469 108°0 
10°0 52:1 113°6 
11:0 57°3 119-2 
12:0 62°5 124°0 
