ASTRONOMY. 
221 
The mathematics of this solution we do not call in question, 
the question with us is, whether there be any sufficient 
reason to believe, that attraction is produced by an eman¬ 
ation. For my part, I am totally at a loss to comprehend 
how particles streaming from a centre should draw a body 
towards it. The impulse, if impulse it be, is all the other 
way. Nor shall we find less difficulty in conceiving a con¬ 
flux of particles, incessantly flowing to a centre, and car¬ 
rying down all bodies along with it, that centre also 
itself being in a state of rapid motion through absolute 
space: for by what source is the stream fed, or what be¬ 
comes of the accumulation? Add to which, that it seems 
to imply a contrariety of properties, to suppose an ethereal 
fluid to act , but not to resist; powerful enough to carry 
down bodies with great force towards a centre, yet, in¬ 
consistently with the nature of inert matter, powerless and 
perfectly yielding with respect to the motions which result 
from the projectile impulse. By calculations drawn from 
ancient notices of eclipses of the moon, we can prove that, 
if such a fluid exist at all, its resistance has had no sensi¬ 
ble effect upon the moon’s motion for two thousand five 
hundred years. The truth is, that, except this one 
circumstance of the variation of the attracting force at 
different distances agreeing with the variation of the 
spissitude, there is no reason whatever to support the 
hypothesis of an emanation; and, as it seems to me, 
almost insuperable reasons against it. 
(*) II. Our second proposition is, that whilst the pos¬ 
sible laws of variation were infinite, the admissible laws, 
or the laws compatible with the preservation of the system, 
lie within narrow limits. If the attracting force had va¬ 
ried according to any direct law of the distance, let it have 
been what it would, great destruction and confusion would 
have taken place. The direct simple proportion of the 
distance would, it is true, have produced an ellipse; but 
the perturbing forces would have acted with so much ad¬ 
vantage, as to be continually changing the dimensions of 
the ellipse, in a manner inconsistent with our terrestrial 
nine times the space. For the same reason if the distance be increased 
four, five, or six times, the area of the shadow will contain sixteen, twenty- 
five, or thirty-six squares, each equal to the object. Now the quantity 
of light which falls upon the object would, if it had not been intercepted, 
have spread over that part of the screen, which is occupied by the shad¬ 
ow; and as the surface is increased, over which a certain quantity of ray9 
is spread, in the same ratio their spissitude or density will be diminished; 
consequently this spissitude will be reciprocally as the squares of the dis¬ 
tances.— Paxton . 
