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POPULAR SCIENCE REVIEW. 
Casella, for portability, makes the arms to fold. The instru- 
ment can be mounted on a piece of gas pipe or otherwise. 
Further, it is available for ascertaining the ventilation of places 
of public resort; an inspection showing at once the progress of 
the current of air circulating above the heads of an audience. 
Lind’s anenometer (Fig. 6.) is a portable and elegant little 
instrument. A column of fluid, descending in a tube of about 
i-inch bore, and ascending one of J-inch bore, shows, on a 
graduated scale, the pressure of the wind on a square foot, and 
its velocity. A light arrow-shaped vane is placed, when required, 
upon a point on the upper edge of the instrument, to indicate 
the coincidence of the mouth-piece with the direction of the 
wind, and a small plummet line, protected by plate glass in the 
body of the scale, indicates the true perpendicular position of 
the instrument. 
Other anenometers in use are. Osier’s, Whewell’s, and Catox’s, 
but, for reasons stated above, the}^ are unsuited to the use of 
amateurs, and therefore I say nothing about them. In the ab- 
sence of an anenometer, it is usual to record the force of the wind 
guessed , rather than estimated, by noting it on a scale of 0 — 10, 
0 representing calm, and 10 a terrific hurricane. The progres- 
sion adopted is usually as follows, but the whole thing is, in 
the highest degree, vague and unsatisfactory : — 
0. Calm. 
1. Motion of air hardly felt. 
2. Light breeze, just perceptible. 
3. Gentle breeze. 
4. Brisk pleasant breeze. 
5. Very brisk breeze : fresh. 
6. High wind. 
7. Rough squally wind. 
8. Very high wind ; gale. 
9. Hurricane ; tempest. 
10. Violent hurricane, tearing up trees, &c. 
In recording the position of the vane no greater nicety need 
be attempted than sixteen points of the compass, N., N.NE., 
NE., E.NE., E., &c. 
An observatory, specially fitted up for meteorological pur- 
poses, will contain divers instruments, with which the popular 
observer has no special concern, such as the electrometer, the 
actinometer, the cyanometer, the evaporating gauge, the ozono- 
meter, &c. For information on points connected with these, 
reference must be made to treatises on meteorology, of which, 
by the way, there is a great dearth. The ordinary amateur will 
