ON MR. WHEWELL’S ANEMOMETER. 161 
a scale fig. 11, graduated into tenths of an inch, and termina- 
ting in a concave rest G, adapted to the register barrel; this 
scale is applied accurately along the barrel on which the pencil 
has registered the amount of wind, as shown in fig. 12. There 
are two sliding-pieces p p on this scale; these are set so as to 
inclose the amount of wind in any given direction and the re- 
sult read off on the scale. This may be also easily effected by a 
fine pair of compasses and a common scale. 
The cover C, fig. 4, is so contrived as to be easily removed at 
any time, being fixed on the plate A by four small studs and a 
clamp screw; a small trap in the roof enables the observer to 
inspect the wheel-work frequently, and occasionally apply a little 
oil to the pivots. The action of the machine is hence preserved 
in a sufficiently uniform state; and I have little doubt that 
the velocity of revolution of the fly may be fairly assumed as 
proportional to that of the wind. The cover C has been found 
to give the wheel-work the required protection, and the instru- 
ment now in operation here is preserved so as to be quite con- 
sistent with itself. It would not be at all difficult to construct 
anemometers, which if attended to in this way would prove very 
comparable with each other, especially if they were all made by 
the same person, or according to the same proportions in every 
respect; and if the respective rates of motion under the same cur- 
rent were compared at first with a standard instrument, a fair 
degree of accuracy must unavoidably be arrived at. The diffi- 
culties in this respect are not greater than those incidental to any 
other machine in which the effects of wheel-work and friction have 
to be considered, as for instance in the rates of different chrono- 
meters. If the different pivots were set in agates, and the point 
of the steel axis of the fly allowed to turn against an agate 
instead of bearing upon a shoulder, the instruments would main- 
tain a very uniform action. 
This valuable instrument being now effectively at work, I trust 
at the next Meeting of the Association, to have completed a 
graphical delineation of the integral amount of wind at this place 
for a whole year without any intermission. 
The sum voted by the Association for the purposes of Osler’s 
Anemometer has been applied in completing the repairs and al- 
terations found requisite; in the expense of tabulating the re- 
sults both of the instrument here and at Birmingham ; and to 
other expenses incidental to the observations now in progress. 
Mr. Osler will be prepared to lay some of the results before the 
Physical Section of the Association. 
The remaining sum entrusted to my care for carrying on the 
original hourly series of Meteorological Observations here, has 
VOL. Ix. 1840. M 
