54 REPORT—1848. 
the highest chemical, developes also the most exalted electrical, phenomena, the 
author infers that chemical and electrical forces and caloric are one and the same 
thing, because the substance developing the highest chemical and electrical powers 
displays also the greatest capacity for, and contains the most intense quantity of 
heat. Thus chemical and electrical forces appear to be only modifications or mani- 
festations of calorific agency. 
The author shows that M. Melloni employs the same arguments for the proof 
of the analogy of light and heat. He adduces certain experiments of Professor 
Draper to show that a strip of platinum heated by the voltaic current corresponds 
with minute precision in the development of light and heat at all times; but that 
author has overlooked the equally manifested analogy of these two forces with the 
force from which they are developed—the fountain whence they are derived—employed 
in these experiments. 
On the peculiar Cooling Effects of Hydrogen and its Compounds in eases of 
Voltaic Ignition. By W.R. Grove, F.R.S. 
This communication was illustrated by an experiment, in which it was shown that 
a platina wire, rendered incandescent by a voltaic current, was cooled far below the 
point of incandescence when immersed in an atmosphere of hydrogen gas. This 
remarkable cooling property of hydrogen of course became the subject of experi- 
mental examination in comparison with other gaseous media. By a peculiar arrange- 
ment, tubes containing coils of platina wire were filled with hydrogen and other 
gases, and then being plunged into water in which delicate thermometers were 
placed, the wires were traversed by the same current from the battery, and it was 
found that the water was always more heated in a given time by the wire in the tubes 
of oxygen, nitrogen, or carbonic acid, than in those of carburetted hydrogen, olefiant 
gas or pure hydrogen. It became necessary now to ascertain the cause of this pe- 
culiar phenomenon of hydrogen. It was found not to be due to specific heat, to 
specific gravity, nor to any conducting power of the gases; and some difficulty was 
found upon examination to exist if it was attempted to refer it to the greater mobility 
of the particles of hydrogen -gas as the lightest known, than of oxygen, nitrogen, 
carbonic acid, &c. It was found that this peculiar property also belonged, but to a 
less extent, to all the hydrocarbonous gases. The author considered it might be 
due to a readiness of convection of heat from the ignited surface, hydrogen being, 
as compared with the other gases, in the same relation to the heated body as a black 
surface is when compared with a white one. 
On the Colouring Matters of Madder. By James Hiccin. 
The author, after describing the three colouring matters of madder, xanthin, ru- 
biacin and alizarin, and the means he employs to separate them in a pure form, pro- 
ceeds to show that the opinion usually entertained—that it is the alizarin only which 
is the valuable part of madder—is incorrect ; and experiments are adduced to prove 
that in proper circumstances, such as obtain in ordinary madder-dyeing, the xanthin 
and rubiacin contribute very materially to the effect. They are shown not ‘to act 
directly, but through becoming changed into alizarin, which then combines with the 
mordants. This change is considered by the author to be induced by a peculiar azo- 
tized ferment, found in madder, whereby xanthin becomes rubiacin and this latter 
alizarin ; and the opinion is held out that all colouring matter in madder is derived 
primarily from xanthin. : a 
On the Influence of Light in preventing Chemical Action. 
By Rozserr Hunt. 
Having called attention to several experiments in which certain luminous rays had 
been found to protect photographic agents from chemical change, particularly in the — | 
researches of Sir John Herschel, the author proceeded to describe his own experi- 
mental investigation of this subject. 
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