804 
DR. OLIVER LODGE OR ABERRATIOR PROBLEMS. 
motion ; or, more simply, there need be no globe at all, but simply a polar axis revolving 
once a day opposite to the earth, and carrying with it a dial with the names of the 
months and days recorded round its circumference, set on the axis at an obliquity of 
23^°, and adjusted once for all to coincide with the ecliptic. The date on the card 
will then point out the line of motion. The clock, if kept to G.M.T., would never 
give the motion more erroneously than a small correction analogous to the equation 
of time. By giving the card one step forward every 29th of February, it could be 
kept right until the whole thing wanted that -j^oth part of a rotation per century 
about a vertical axis which precession demands. [My assistant, Mr. E. E. Bobixsox, 
has connected a clock through a Hooke’s joint with a pointer which moves so as very 
fairly to indicate the direction of orbital motion at any instant.] 
Electrical methods of detecting Motion through Ether. 
77. It might j)erhaps appear possible that electrical methods may succeed in 
showing a first-order effect of terrestrial motion, since charged bodies in motion repel 
each other with modified force. 
It is not possible to control or vary it except by combining the above several kinds 
of movement, and Fitzgerald has suggested a plan of observing whatever eflkct raav 
be caused by the alternate agreement and disagreement between the earth’s orbital 
motion and the solar system’s proper motion : say by measuring the attraction of 
charged parallel plates at intervals of six months. 
But, inasmuch as the force between charged bodies is independent of the direction of 
their motion, or (otherwise) because the electrical attraction between parallel moving 
charges depends on the product of their velocities, it must be the second-order of 
aberration magnitude that is really involved. 
Description of Plates 31 axd 32. 
Plate 31. Details of optical frame, showing the mode of supporting the mirrors, both 
the silvered and the semi-transparent. 
Plate 32. Details of whirling machine, showing the pair of steel disks, 1 yard in 
diameter, driven by an electric motor. 
