( 678 ) 
But, for this system, by (22), joined to the 5 and 7 of the 
equations (4), 
1 
DT se 
so that we find by using (21) 
meld rekt tE el 
G O~ Cc" O 
This is precisely the formula (7), if for & we take the value (3). 
Physics. — H. A. Lorentz. “The intensity of radiation and the 
motion of the earth”. 
(Communicated in the meeting of March 29, 1902). 
Many years ago Fizeau') remarked that, if the aether does not 
follow the earth in its annual motion, the radiation, emitted by a 
terrestrial source of light or heat Z, might possibly have unequal 
intensities in different directions. Let A be a point that is likewise 
fixed to the earth, and whose distance from Z we shall denote by /. 
Then, if ZA have the direction of the earth’s velocity v, a vibration 
produced by Z will have to travel over a length 
ns 
RT 
(e velocity of light), before it reaches A. On the contrary, its course 
will be 
Pati 
ce dv 
if LA has the opposite direction. Frzeau expected that the intensities 
received by 4 in the two cases would be inversely as the squares 
of these expressions, so that there would be a difference which one 
might hope to detect by means of suitable experiments with a thermo- 
electric battery. 
From our present views regarding electric and optical phenomena 
in moving bodies it may be inferred that the experiment, proposed 
by Fizeau would have a negative result, the amount of heat which 
is imparted to an absorbing body being independent of the earth’s 
motion. 
It will suffice to consider a simple case, omitting all terms depending 
1) Pogg. Ann., Bd. 92, p. 652, 1854. 
