130 Davis — Miniature Anemometer for 



hollow half-cylinder. The half-cylinder cups were mounted 

 on the ends of four cardboard arms, in the center of which was 

 a glass pivot by which the whole arrangement was supported 

 on the point of a fine needle. Three anemometers were con- 

 structed bearing cups of three sizes. These anemometers will 

 be referred to in this paper by the trade numbers of the 

 capsules from which they were made. 



Anemometer No. 00 carried four cups, each of which was 

 •75 cm in diameter and 2 cm long. 



Anemometer No. 2 carried eight cups, two on each arm, each 

 of which was *58 cm in diameter and l-4 cm long. 



Anemometer No. 5 carried eight cups, two on each arm, each 

 of which was *45 cm in diameter and '8 cm long. 



In conducting the experiments a stroboscopic disc was used 

 to count the revolutions of the anemometers ; also a mercury 

 manometer was employed to obtain the same pressure of blow- 

 ing the pipe throughout the experiments. 



The mean results of a number of experiments are given in 

 the tables below : 



Anemometer No. 00. 

 Position in pipe. Eate of rotation. 







5 1*45 



10 5'71 



15 9-09 



20 -- 10- 



25 10-9 



30 10-34 



35 ._ 9-95 



40 - 7-79 



45 3-80 



52 -.. 



Anemometer No. 2. 



Position in pipe. Rate of rotation. 







5 1-66 



10 - 6*46 



15 . 9-21 



20 10'55 



25 11*3 



30 10*8 



35 _ _ 10-25 



40 7-52 



45 3-1 



52 .1 ._ 



