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Aa=0 
Ae= 0,018 0? + 1,38 0 0’ 
A 0,95 Ò? 4 0,28 0 0' 
p= 
A0O= 7,60 02 — 4,260 0' 
Ae = — 0,09 Ò? + 1,95 0 0’ 
Az' = — 6,82 d2— 1,930 0 
Now, 0'’=1,6X10-+ and, if we put 0=5,3 X 10-5, we get 
Ree tt loer Ag = ot MELD 
AO = 187 O10). “Aro == 10E TOO Ae = 1855 TO 
The changes that take place in a century are found from these 
numbers, if we multiply them by 415, and, if the variations of y, 0, 
@ and z' are to be expressed in seconds, we have to introduce the 
factor 2,06 10°. The result is, that the changes in p, 0, @ and z' 
amount to a few seconds, and that in e to 0,000005. 
Hence we conclude that our modification of Newron’s law can- 
not account for the observed inequality in the longitude of the 
perihelion — as WEBER’s law can to some extent do — but that, 
if we do not pretend to explain this inequality by an alteration of 
the law of attraction, there is nothing against the proposed formulae. 
Of course it will be necessary to apply them to other heavenly 
bodies, though it seems scarcely probable that there will be found 
any case in which the additional terms have an appreciable influence. 
The special form of these terms may perhaps be modified. Yet, 
what has been said is sufficient to show that gravitation may be 
attributed to actions which are propagated with no greater velocity 
than that of light. 
As is well known, LaAPLACE has been the first to discuss this 
question of the velocity of propagation of universal attraction, and 
later astronomers have often treated the same problem. Let a body 
B be attracted by a body A, moving with the velocity p. Then, if 
the action is propagated with a finite velocity V, the influence 
which reaches B at time ¢, will have been emitted by A at an anterior 
moment, say t—vt. Let A, be the position of the acting body at 
this moment, A, that at time t. It is an easy matter to calculate 
the distance between these positions. Now, if the action at time 
