PHYSICS — BARNETT, BURGEISS. 211 



actual capacity of the ebonite cylinder, so far as this depends on the tubes of 

 displacement stretching between the outer coat and the inner cylinder ; S' is 

 the capacity of the tubes stretching betwen the outer coat and the case, but 

 does not include the capacity vS*'' of the tubes stretching between the brushes, 

 connecting wires, electrometer quadrants, condenser plate, etc., and the 

 earth, the coat of the ebonite being the only one of these conductors in 

 motion ; F' is the mean voltage from the insulated electrometer quadrants to 

 the outer surface of the outer coat of the ebonite in motion in the magnetic 

 field; do is the electrometer deflection when the outer coat (at rest) and con- 

 nections have the total change q^ ; and d is the electrometer deflection pro- 

 duced when the ebonite rotates in the magnetic field. Instead of ^o, Wilson 

 has what he considered the actual capacity the condenser would have with 

 air substituted for ebonite, so far as lines of displacement stretching between 

 the outer coat and the inner coat are concerned ; for S' he has S^ -\- 5"'. 

 Neither one of these quantities was determined. It is therefore impossible 

 to say what difference exists between Wilson's results and those called for by 

 Lorentz's theory. Attention has already been called to another error in 

 Wilson's theory, which, however, while it made the statement of one of his 

 conclusions and of Lorentz's theory incorrect, did not affect his calculations.* 



A difficulty which Wilson apparently considered one of the greatest he 

 met in the experimental work, he judged to arise from the abrasion of metal 

 at the insulated brush. This and with it the troublesome terms 5" and V\ 

 in formula (3) can both be eliminated by surrounding the rotating cylinder 

 and insulated brush with a second cylinder, also connected with the elec- 

 trometer. 



It is expected that this investigation will be completed and ready for pub- 

 lication in the early winter. All serious difficulties appear now to have been 

 overcome. 



Burgess, Charles F., University of Wisconsin, Madison, Wisconsin. Grant 

 No. 430. Investigation of the properties of electrolytic iron and alloys 

 made from it. ( For previous reports see Year Book No. 4, pp. 247-249, 

 and Year Book No. 5, pp- 224, 225.) $2,500. 



This work has been carried on in the AppHed Electrochemistry Laboratories 

 of the University of Wisconsin and has progressed with practically no inter- 

 ruptions during the past year. Until June i, 1907, Dr. Oliver P. Watts 

 devoted a portion of his time to the investigation, and he was assisted dur- 

 ing the past year by Mr. O. L. Kowalke, who, from June i to the present 

 time, has had charge of the work. Various assistants have been employed 

 from time to time, such assistants having been chosen from among the 

 advanced students. 



* S. J. Barnett, Royal Soc. Proceedings. Series A, 1905. 



