Constancy of Velocity of Light emitted by Moving Source. 147 



per second of the revolutions. It is known that the centri- 

 fugal velocity increases as the square of that number, and 

 the velocity of displacement grows as the first power. After 

 different attempts I fixed the diameter at 2 m. : because 

 since the small tubes with the mercury weigh 35 gr., the 

 centrifugal force that excites them at a velocity of only 

 14 revolutions per second (corresponding to nearly 90 m. 

 of peripheral velocity) amounts to 30 kg. 



That is nearly the highest point of capacity of charge to 

 which the glass material can be brought. In my experiments 

 the glass tubes still broke very often, although allowing a 

 sufficient interval of time for the observation and measures. 



In respect to the resistance of air, it has been reduced to 

 the minimum by using fine steel wires of high mechanical 

 resistance as connexions between the tubes and the rotating 

 axle. Notwithstanding the aforesaid conditions of velocity, 

 the apparatus being provided with only two tubes in diametral 

 position, a power of about 5 kw. was necessary. I give now 

 a short description of it. The figure illustrates schematically 



the details, not presenting them on a uniform scale. is the 

 rotating axle connected with a pulley and strap to a motor 

 with velocity of rotation capable of regulation and inversion, 

 and of the maximum power 10 H.P. Two airless tubes of a 



L2 



