344 : REPORT—1846. 
Lind’s anemometer corresponds to the space from 0:0 to 0°10 inch, and to a 
velocity of from 0 to 15 feet per second, that is to say, 0 to 10 miles per 
hour*, 
Except the instrument be very carefully constructed, this degree of accu- 
racy is unattainable, and pressures less than 1b. per foot, and velocities of 
several miles per hour, may not be recorded at all. One of the most inter- 
esting of the powers connected with the use of this instrument has been 
already noticed,—the power of studying the momentary phases of air-move- 
ment at the observatory. This is peculiar to the principle of Mr. Osler’s 
invention ; another result of great importance has been derived from the study 
of its tracings. The force of the wind for every hour of the day and night 
has been determined not only for the whole air-movement, but for each direc- 
tion of wind, and in each season of the year. Mr. Osler’s conclusions on 
this subject, supported by Harris, Brewster and Sabine, go directly to deter- 
mine a law of the wind’s daily pressure and to connect it with the progress 
of diurnal heat. In fact the curves of daily wind-force and of daily mean 
temperature are almost identical, as may be seen in Col. Sabine’s Observations 
on the Meteorology of Toronto. 
The same registration gives data for investigating what may be called 
curves of storm pressure, the law according to which wind-pressure rises to 
a maximum and sinks to a minimum, a subject of great interest and import- 
ance. From some data which may be found in Mr. Osler’s Report, in the 
volume of the Association for 1840, I have obtained the following Table of 
pressures during a strong wind of 96 hours’ duration. 
* Tt may be useful to give here Smeaton’s Table of Wind Velocity in relation to Pressure 
in Ibs. (Phil. Trans. 1759.) 
Velocity of Wind. Pressure on 
Ta VE ACI comes | hance omg 
} . avolr- . 
— bet pe ae Se-| ™ pats 
1 1:47 005 Hardly perceptible. 
2 2°93 020 Taat tibl 
3 4-40 044 ust perceptible. 
: 0 mee } Gentle pleasant wind. 
10 14°67 *492 . 
15 22-00 1107 | Pleasant brisk gale. 
20 29°34 1:968 a as 
25 36°67 3-075 a 
30 44:01 4:429 3 
35 51°34 6-027 } Bigh wind. 
40 58°68 7°873 ; 
45 66-01 9-963 } Very high. 
50 73°35 12:300 Storm or tempest. 
60 88-02 17°715 Great storm. 
80 117°36 31°490 Hurricane. 
100 146°70 49-200 Destructive hurricane. 
913°6 1340* | One atmosph. 
Vh atmosphere in feet x 83, = feet per second, 
