EXPERIMENT ON VELOCITY. 243 
ject to universal attraction; it would with difficulty be 
darted out from an incandescent body, because the attrac- 
tion of that body will tend to carry it back again ; hence 
a gradual diminution of its original velocity must un- 
doubtedly take place; it is only necessary to inquire 
whether obsérvation can enable us to discover it. It 
would be a simple question of calculation how, in mak- 
ing some suppositions with respect to the physical con- 
stitution of certain fixed stars in respect to their size and 
density, which do not appear extravagant, we find that 
they may, by their attractive force, annihilate altogether 
the velocity of emission of luminous molecules; that 
after having proceeded to a given distance, these mole- 
cules, which had so far separated themselves from the 
body, must return thither by a retrograde movement. 
Thus, certain stars might be as luminous as the sun, to 
the distance of 40,000,000 leagues, for example, and 
beyond that be altogether dark ; that distance being the 
exact limit beyond which none of their rays could pass. 
If we change considerably the volumes and densities 
which give these results; if we assume for stars of the 
first magnitude such dimensions as no astronomer would 
refuse to consider as probable, they will no longer pre- 
sent such strange phenomena, they will no longer be 
dazzling at this distance, and completely dark at a little 
farther distance; but the velocity of their light will 
change with the distance ; and if two such stars are at 
very different distances from the earth, their rays will 
arrive at our eyes with dissimilar velocities. Is it not 
then a formidable objection against the theory of emis- 
sion, that there should be this perfect equality of velocity 
in all cases, which all observations testify ? 
There exist very simple means for altering to a nota- 
