Negative charge - 
224 Capt. Abney and Lieut.-Col. Festing on the Relations 
Mercury at Mercury at 
rooin-tenip. 360° C. 
■r, ... , f — 2 scale-div. +3*75 scale-div. 
Positive charge < 
f-4 „ +5 
I „ +3 
In both methods the mercury, when rapidly evaporating, 
condensed in drops upon the platinum disk C. Since, accord- 
ing to the present view, a molecule of mercury contains but 
one atom of mercury, the result of this experiment is the most 
conclusive of the proofs against the hypothesis investigated by 
these experiments, and which has been universally held to the 
present time. This result with mercury, agreeing as it does 
with the results obtained with the other liquids used, is totally 
opposed to the hypothesis hitherto entertained, and justifies 
the assertion that the vapour arising from electrified still sur- 
faces of liquids is electrically neutral. 
Physical Institute, Berlin, 
March 7, 1883. 
XXXII. An Investigation into the Relations between Radiation, 
Energy, and ' Temperature. By Captain Abxey, R.E., 
F.R.S., and Lieut.-Col. Festing, R.E* 
IN the course of researches on the subject of atmospheric 
absorption of solar radiation, on which we have for some 
time past been engaged, it incidentally became desirable to 
ascertain the relation between the radiation from a black body 
and its temperature — a subject which, though well worn, is by 
no means exhausted. Sir William Siemens has made the most 
recent contribution to this subject in a paper lately communi- 
cated to the Royal Society, in which he describes his endea- 
vour to solve the question by noting the increase of electrical 
resistance of platinum wire with increased temperature and 
by taking the relationship of energy to resistance — a method 
of much promise, but which appears to us to be defective for 
the following reasons. Platinum wire is not black at ordinary 
temperatures, and it is at least doubtful whether it is such a 
good radiator as carbon : and, secondly, much of the energy 
must have been dissipated by convection- currents. 
It has, however, struck us that a continuation of the experi- 
* Communicated by the Authors. 
