FOR THE SCIENCE OF CALORIFIC RADIATIONS. 533 
significant expression than that which is at present used, since 
the idea of colour necessarily includes that of the radiating form 
and of a heterogeneous constitution, but we introduce into the 
study of physics a term more conformable to the great end 
to which scientific nomenclatures tend, namely the property 
of continually calling to our mind the generalities of the 
group of phenomena which is under consideration. In fact, 
the intimate bond established between the idea of colour and 
that of calorific radiation, does not allow us for a single instant 
to lose sight of the principle which serves as a basis and sum- 
mary for the properties newly discovered regarding radiant heat, 
a simple and prolific principle, which brings facts the most un- 
like near to each other, so that it is sufficient to call to mind 
that there exists in the calorific rays, and in bodies endowed 
with the greatest limpidity, or with the greatest degree of white- 
‘ness, a quality invisible, but entirely analogous to coloration, in 
_ order to predict or explain all the series of the phenomena of 
transmission, of diffusion and of absorption, which the science 
_ of calorific radiations now presents*. 
Coloration once adopted as a distinguishing character of ra- 
diant heat, it is evident that it should form the fundamental 
basis of the language relative to this branch of science: I have 
endeavoured to fulfill this condition in my attempt at nomencla- 
ture. In fact the word thermochrosis, which I use to designate 
this coloration of bodies or of calorific rays, comes from the same 
radicals whence the expression Thermochroology + is derived, as 
well as the adjectives thermochroic, coloured for heat, and ather- 
mochroic{, without colour of heat. From the Greek word for 
black§, I name those bodies melanothermic which absorb all 
_ kinds of calorific radiations energetically and in equal propor- 
tions, acting thus upon heat as black substances act upon light. 
Those substances, on the contrary, which disperse the different 
* «Every physical science,” says Lavoisier, “is necessarily formed of three 
things,—the series of facts which constitute the science, the ideas which call 
them to mind, the words which express them. The word should give birth to 
the idea, the idea depict the fact: they are three impressions of one seal.” The 
denomination thermochroology and its derivatives answer exceedingly well, 
if I do not deceive myself, to the three conditions proclaimed by the great 
legislator of chemistry. 
+ From deoucs hot, [heat] and xecx colour; whence the verb yedw to colour, 
and yeaors coloration. 
} From a privative, and S:guoxeoixds coloured for heat. 
§ From perus, gen. wercvos black. 
