Intelligence arid Miscellaneous Articles, 571 



3?;By making water move in the two tubes at the same time and in 

 contrary directions in each, it will be seen that the effects should be 

 added. This double current having been produced, the direction 

 maybe again reversed simultaneously in the two tubes,' and the 

 eflfect would again be double. IS '• 



All the movements of the water were produced in a very simple 

 manner, each tube being connected by two conduits situated near 

 their extremities, with two reservoirs of glass, in which a pressure 

 is alternately exercised by means of compressed air. By means of 

 this pressure the water passes from one reservoir to the other by 

 traversing the tube, the two extremities of which are closed by the 

 mirrors. The interior diameter of the tubes was 5™™* 3, their length 

 i*l'-487. They were of glass. 



jrf'.The pressure under which the flowing of the water took plac^ 

 ftiight have exceeded two atmospheres. The velocity was calculated 

 by dividing the volume of water running in one second by the area 

 of the section of the tube. I ought to mention, in order to prevent an 

 objection which might be made, that great care was taken to obviate 

 the effects of the accidental motions which the pressure or the shock 

 of the water might produce. Therefore the two tubes, and the 

 reservoirs in which the motion of the water was made, were sus- 

 tained by supports independent of the other parts of the apparatus, 

 and especially of the two lunettes ; it was therefore only the two 

 tubes which could suffer any accidental movement ; but both theory 

 and practice have proved that the motion or flexions of the tubes 

 alone were without influence upon the position of the fringes. The 

 following are the results obtained. 



When the water is set in motion the fringes are displaced, and 

 according as the water moves in the one direction or the other, the 

 displacement takes place towards the right or the left. 



The fringes are displaced towards the right when the water is run- 

 ning from the observer in the tube situated to his right, and towards 

 the observer in the tube situated to his left. 



The fringes are displaced towards the left when the direction of 

 the current in each tube takes place in a direction opposed to that 

 which has just been described. 



With a velocity of the water equal to 2"^* a second, the displace- 

 ment is already very sensible ; with a velocity of 4 to 7 metres it is 

 perfectly measurable. 



After having demonstrated the existence of the phsenomenon, I 

 endeavoured to determine its numerical value with all the exactitude 

 which it was possible to attain. 



By calling that the simple displacement which was produced when 

 the water at rest in the commencement was set in motion, and that 

 the double displacement which was produced when the motion was 

 changed to a contrary one, it was found that the average deduced 

 from nineteen observations sufficiently concurring, was 0"23 for the 

 simple displacement, which gives 0*46 for the double displacement, 

 the width of a fringe being taken asounity. The velocity oi the 

 water was 7*069 metres a second. > oj) vb-j; yri.t -jiifivr ^noiJom ■pnii lo 

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