84 THE ROYAL SOCIETY OF CANADA 



Dines Pressure Tube Anemometer 



Dines in the course of his experiments designed a pressure tube 

 anemometer by which the velocity of the wind is measured by its 

 pressure. The instrument is described by himself and by instrument 

 makers, so that only a brief description of it is given. It is shown 

 diagrammatically in Fig. 1. The mouth of the tube A is held into the 

 wind by the wind vane and connects through tubing with the regis- 

 tering apparatus. On the vertical tube at D, several rows of small 

 holes are bored and the wind blowing across these produces a suction 

 which is communicated to the recording apparatus through another 

 tube. The recording apparatus consists of a specially designed float 

 F; the tube A connects through P to the inside of the float and the tube 

 C through S to the reservoir at the top of the float, and as A 

 produces a pressure and C a suction, they both act together to raise 

 the float; the rise and fall of the float are recorded on the drum E. 

 The pressure of the wind varies as the square of the velocity and the 

 float is so designed that the amount of its rise or fall is proportional to 

 the velocity of the wind ; the scale of velocity is thus linear. The re- 

 lation between the pressure and wind velocity as deduced by Dines in 

 his experiments is 



P=-003 v2 



when P is the pressure in lbs. per square foot, and v the velocity of 

 the wind in statute miles per hour. 



The charts are graduated according to the results of Dines' 

 experiments on an empirical basis, but the indications of the different 

 instruments can be compared with a pressure gauge and so calibrated 

 as follows: 



One end of a U tube half filled with water is connected to the 

 inside of the float so as to be air-tight and provided with a means to 

 alter the pressure. The other end of the U tube and the reservoir 

 above the float is left open to the air in the room. If now the pressure 

 of the air inside the float and the arm of the U tube with which it is 

 connected is increased, the increase of pressure can be measured by 

 the difference in the level of the water in the two arms of the U tube 

 and the velocity to which the pressure corresponds is given by the pen 

 on the recording chart. If the instrument is properly constructed 

 and thoroughly adjusted the relation h/V^ where h is the difference in 

 level of the water in the U tube and V is the velocity in miles per hour 



