﻿970 Dr. Thomas on Discharge of Air through Small 



and outlet to the jacket. The pressure of the air in the tube 

 A at a distance of about 1*5 inches above the orifice was 

 determined by means of the tube C, which was closed at its 

 lower end and provided with a number of small circular 

 openings on its cylindrical surface near its lower end. The 

 tube C was connected with a water manometer, which was 

 read to 1/50 mm. by means of a cathetometer microscope. 

 Calculation showed that the deficit of pressure due to motion 

 of the air in A was negligible. Air delivered from the 

 orifice B passed downwards through the tube D, of vertical 

 length about 10 inches, and bent as shown. The lower end 

 of D was shielded by a large open box, so that disturbances 



I 



-^ 



-Ea 



■ft 



B 



I i I i I i I 



in the air of the laboratory were very largely prevented from 

 affecting the jet *. No Yenturi tube, to increase the air- 

 entrainment, was inserted in Din the present series of experi- 

 ments, as it was found that the same tube was not equally 

 suitable for use with all the orifices employed. 



(b) The Air Induction lube. — Air set in motion by the 

 action of the jet issuing from the orifice flowed towards the 

 jet through the flow tube E, in which was placed a hot-wire 

 anemometer of the Morris type, constituted of two fine 



* It may be remarked that without such protection, the effect of any 

 atmospheric disturbance upon the indication of the hot-wire anemometer 

 employed is under certain conditions considerably magnified by the 

 operation of the jet. A combination of jet and hot wire, such as 

 described herein, would appear to be an exceedingly sensitive device for 

 indicating small atmospheric movements. 



