Vol. 8, 1922 
PHYSICS: H. A. LORENTZ 
333 
in 1914, showing a decidedly lower transmission of radiation through the 
water cell, in the case of Venus and Saturn. 
The intensity of the planetary radiation increases with decrease in the 
density of the surrounding atmosphere and (as interpreted from the water 
cell transmissions) in per cent of the total radiation emitted, is as follows: 
Jupiter (O), Venus (5), Saturn (15), Mars (30) and the Moon (80). 
The water cell transmission of the radiations from the southern (50.6%) 
and northern (53.1%) hemispheres of Mars should be and is higher than 
that of the radiations emanating from the equatorial (47.3%) region, 
owing. to the depletion of the reradiated energy by the greater air mass. 
Moreover, the intensity of the planetary radiation from the northern 
hemisphere of Mars was found to be less than from the southern hemis- 
phere. This is to be expected in view of the observed cloudiness over the 
northern hemisphere which is usually the brighter and is approaching 
the winter season, and hence is at a lower superficial temperature. 
These data were obtained through the generosity of the Lowell Observa- 
tory, Flagstaff, Arizona, who financed this research. Dr. C. O. Lampland 
again kindly operated the telescope and it is intended to publish the com- 
plete results in a joint paper on the measurements of planetary radiation 
and their astronomical significance. 
As already stated, the object of the present note is primarily to place 
on record a verification of the results, obtained a year ago, on stellar tem- 
peratures. 
1 Proc. Nat. Acad. Sci., 8, 1922 (49-53). 
2 Bureau of Standards Scientific Paper, No. 438, 1922. 
PROOF OF A THEOREM DUE TO HEAVISIDE^ 
By H. a. Lorentz 
Haarlem, Holland 
Communicated August 7, 1922 
In the Electrical Papers, Vol. 2, p. 412, Heaviside states: "The whole 
work done by impressed forces suddenly started exceeds the amount repre- 
senting the waste by Joule-heating at the final rate (when there is any), 
supposed to start at once, by twice the excess of the electric over the 
magnetic energy of the steady field set up." 
Consider a system of bodies, either conductors or dielectrics, or, for the 
sake of generality, both at the same time, and denote by E the electric 
force, by H the magnetic force, by D the dielectric displacement, by C 
