The question whether this cause modifies gravitation admits of an easy test from observation.
The question has also been raised whether the action of gravitation is absolutely instantaneous.
On the other hand the enigmatical motion of the perihelion of Mercury has not yet found any plausible explanation except on the hypothesis that the gravitation of the sun diminishes at a rate slightly greater than that of the inverse square - the most simple modification being to suppose that instead of the exponent of the distance being exactly - 2, it is - 2.000 000 161 2.
The meteors, whatever their dimensions, must have motions around the sun in obedience to the law of gravitation in the same manner as planets and comets - that is, in conic sections of which the sun is always at one focus.
A good deal of this is transported by gravitation from Baku to Batum on the Black Sea by means of a pipe laid overland.