2 Trans. Acad. Sci. of St. Louis. 



occur in a revolution, the balancing knob was displaced 

 along the shaft. This results in another unbalanced mo- 

 ment which must be carried by the pivots on which the 

 shaft is mounted. It was estimated that the pivots would 

 at 800 revolutions per second, have carried lateral revolv- 

 ing thrusts amounting to 75 or 80 pounds. It was there- 

 fore determined to repeat this work. Through the cour- 

 tesy of the Department of Physics of the University of 

 Chicago the construction of a rotating mirror was se- 

 cured from patterns used in the building of a mirror for 

 that department. A mile of wire was contributed by the 

 Kinloch Telephone Company of St. Louis, and Wheat- 

 stone's line was reproduced in the hallway of Eads Hall 

 at Washington University. The reflected images of the 

 sparks on the spark board were thrown into a large copy- 

 ing camera. Datum sparks when the mirror was at rest 

 could thus be obtained, and the sparks produced during 

 rotation could also be obtained. When both terminals of 

 the large 8-plate influence machine were put to the line 

 it was found impossible to obtain Wheatstone's result. A 

 series of small sparks was shown in the end gaps at the 

 machine terminals, followed by a single spark in the mid- 

 dle gap. Finally one end of the line was grounded and 

 the other presented to either terminal of the machine. It 

 was then found that when either the positive or the nega- 

 tive discharge was sent through the line, the spark near- 

 est to the machine occurred first, the middle spark sec- 

 ond, and the spark nearest to the ground occurred last. 

 The sparks came at regular time intervals. Wheatstone's 

 conclusion was therefore verified. 2 



The question then arises, are these disturbances dis- 

 charges of the positive and negative fluids, or are they 

 disturbances in the nature of compression and rarefac- 

 tion waves in a fluid? Wheatstone's result does not de- 

 cide between these two possible hypotheses. Rowland's 



2 Probably Wheatstone's drawings represent apparatus used in pre- 

 liminary work, and not the apparatus which he finally used for obtaining 

 his published results. 



