ON THE ANEMOMETERS OF PLYMOUTH. 



251 



usual form of balance-gauges, so that when one compartment is full the ba- 

 lance oversets and allows the other compartment to go on filling; a recipro- 

 cating motion is thus produced, by which an axis is caused to work in a 

 toothed wheel (not seen in the figure) under the disc t, causing it to re- 

 volve through a space proportionate to the quantity of rain delivered at each 

 tip of the gauge N. 



I M a- is a rod set on friction-rollers at u and a;; it is furnished with a rack, 

 I u, to receive the single tooth of a horizontal rod, i/, projecting horizontally 

 from the centre of the clock j/. There are twenty-four teeth in the rack, and 

 thus the rod is moved hourly one division ; by this motion three pencils, 

 numbered in the figure 1, 2, 3, are hourly moved upon the respective discs 

 Its, so that traces are obtained of the direction and velocity of the wind 

 and of the rain for every hour as the discs move under the pencils. 



This instrument is reported to have stood severe gales without having sus- 

 tained any damage, and to have answered very perfectly. The following 

 are some results of its operation from November 184-3 to November IS^^. 



Table A. 



Showing Hourly Velocity of Wind by Foster's Anemometer, from 

 November 1843 to November 1844. 



Table B. 



Showing the Total and Mean Hourly Velocity of each Wind in 

 miles, by Foster's Anemometer. 



Points of 

 Compass. 



Total Velocity 



in miles per 



hour. 



Number of 



hours of each 



wind. 



Mean Hourly 



Velocity in 



miles. 



Points of 

 Compass. 



Total Velocity 



in miles per 



hour. 



Number of 



hours of each 



wind. 



Mean Hourly 



Velocity in 



miles. 



N.N.E. 



N.E. 

 E.N.E. 



E. 

 E.S.E. 



S.E. 

 S.S.E. 



432 



3828 



4468 



2491 



948 



854 



699 



1125 



42 



354 



317 



147 



75 



68 



81 



77 



10-3 

 106 

 14-2 

 17- 

 12-6 

 12-5 

 8-6 

 14-6 



s.s.w. 



s.w. 



w.s.w. 



w. 



W.N.W. 



N.W. 



N.N.W. 



1811 

 2787 

 5773 



10227 

 6836 



16301 

 6695 

 3011 



136 

 149 

 265 

 609 

 383 

 877 

 412 



13-3 

 18-7 

 21-8 

 170 

 170 

 18-5 

 16-2 

 101 



Mr. Foster has estimated the general direction and magnitude of the re- 

 sultant in the following way : — One-half the velocities of north-west and 

 north-east winds are taken and added to the velocities of the intermediate 

 points, calling the total north. 



