‘622 Prof. J. Larmor on the ascertained Absence 
second system, referred of course to axes of co-ordinates 
moving along with it, can be reduced to the form belonging 
to the same system at rest, by the transformation first 
developed by Lorentz: namely, each point in space is to have 
its own origin from which time is measured, its “local time”’ 
in Lorentz’s phraseology, and then the values of the electric 
and magnetic vectors 
(fs Gy h) ames (Ca, ubsre), 
at all points in the ether between the molecules in the system 
at rest, are the same as those of the vectors 
(A J- eee h+ a?) and (a, b+4vh, e—4zvq) 
‘at the corresponding points in the convected system at the 
same local times. This correspondence can, in fact, be 
‘shown to locate the electrons at corresponding points in the 
two systems, and to make them equal ; if, then, they are held 
in rigid connexion, or more generally if their states of 
orbital motion in the molecules are conserved, the effect of 
translatory motion of the system with velocity v is to trans- 
form the ethereal field around them and between them as 
here specified. The fields of ethereal activity are not identical, 
but where one vanishes at any point so does the other at the 
same point. This conclusion was reached by Lorentz, who 
pointed out that it carried with 1t a null result for all recog- 
nizable optical tests of convection in the system, up to the 
first order, with the one exception of the Doppler effect 
which is involved in the “local”? time measurements, and 
which is only a partial exception because it refers to radiation 
coming from outside the system. 
Does, however, the system of electrons need to be constrained 
in order to prevent change of configuration when being con- 
vected ? The force acting on an individual electron @é is 
thereby changed from 
” U cde ae: 
Aqro7e (J Oe Amc? Cy pas aan to 47707e(f, Yd; h). 
If there is a magnetic field (a, 0, ¢) there will thus be 
alteration: if there is no sensible average magnetic field, even 
among the molecules, we may perhaps fairly assume, with 
Lorentz, that no constraint is needed in order to preventchange 
in molecular configuration in the system due to convection. 
Anyhow, the absence of recognizable optical result to the 
first order is certain, as the physical constants of the system 
in bulk must be unaltered to that order. 
But the brilliant experimenting of Michelson and Morley 
