XXIII—ON ELECTROMAGNETIC EFFECTS DUE TO THE MOTION 
OF THE EARTH. By Guo, Fras, FirzGuraup, M.A., F.7.¢.D., ERAsMUS SMITH’S 
Proressor oF ExperiMeNTAL Scrence IN THE University or DUBLIN. 
[Read May 5th, 1882. ] 
Professor Rowland has shown experimentally that a quantity of electricity 
moving acts like an electric current. This had been assumed by many physicists. 
It follows that two quantities of electricity moving in the same direction and with 
the velocity of light, would have no action on one another ; their electrostatic 
action being balanced by an equal and opposite electrokinetic action. As it is very 
unlikely that anything depends on absolute motion, the motion here spoken of 
must be with respect to something, and this something can hardly be any other 
thing than what is known as the ether in space. 
All electromagnetic measurements are made on the surface of the earth, which is 
moving in a threefold way through space. The earth is rotating on its axis, and its 
equatorial surface is moving at the rate of 4°65 x 10‘c.m. per sec, It is moving 
round the sun at the rate of 2°96 x 10° ¢.m. per sec. It is moving with the whole 
solar system through space, at about the same rate, 
Professor Stokes has shown that aberration would be the same, whether the 
ether near the earth be carried along with it or no. Fizeau’s experiments, however, 
show that matter does not carry the ether along with it except to an extent 
depending on the refractive index of the matter. It would follow that no appreciable 
part of the ether in the air moves with the earth. 
All electrostatic measurements should show a twofold periodicity ; one diurnal, 
the other annual. The velocity of the electricity through the ether is different at 
different times of the day, owing to its motion due to the rotation of the earth 
being sometimes added, and sometimes subtracted, from its other motions. It is 
different at different times of the year, owing to the velocity of the earth round the 
sun being sometimes added to and sometimes subtracted from the component along 
the ecliptic of the solar system’s velocity in space. Thevelocity of light is 3 x 10cm. 
per sec., and the daily variation of velocity would consequently change electrostatic 
attractions by the 3°1 x 10—° of their amount, and the annual variation would 
vhange them by about the 1:5 x 10~‘ of their amount. These quantities do not 
seem beyond the possibility of observation with specially constructed instruments. 
It has been supposed that in conformity with these electrostatic actions, there 
TRANS. ROY. DUB. SOC., N.S., VOL. I. 3H 
