"Light had long been supposed to move with a velocity physically infinite, but the late M. Roemer of the Royal Academy of Paris discovered the contrary... But however natural this theory might be, and however well it might be supported, it was then thought too bold, and poor Roemer did not live to see it adopted. It has, however, been since universally a agreed, that the motion of light is successive; and upon this successive motion of light, Mr. Bradley built his explanation of the irregular variations which he had observed in the stars, and which he called their aberation. His theory was this: Let us suppose a series of very small particles, united into a thread, to fall in direction perpendicular to the horizon; and let several of these threads of particles fall at the same time, in he same direction, so as to be parallel to each other, in the same manner as drops of rain in a dead calm. Let us then suppose a tube to be placed in this rain, in a vertical position, and it is manifest that the drop of water which enters the aperture at the upper end of it, will issue at the aperture below, without touching the inside of the tube. But if the tube be moved parallel to itself, though still kept in a position parallel to the direction of the water, it is clear, that this motion of the tube will cause the drop that enters it to touch one of its sides, before it gets to the bottom; and that this contact will happen sooner, in proportion as the motion of the drops is slow, compared with the motion of the tube; and it is easy to demonstrate, that if the motion of the tube, and that of the rain are equal, the drop which falls in the center of the upper aperture of the tube, will come in contact with the inside of the tube, when it has passed down the tube the distance of half its diameter; and, consequently, that the line of its direction will make an angle of five and forty degrees with the axis of the tube: It follows, therefore, that, to prevent the drops of water from touching the inside of the tube, notwithstanding its motion, the tube must be inclined in an angle of five and forty degrees, on the side towards which it moves; and that, if this inclination should be successively made round in the circumference of a circle, the tube would describe round the vertical line, drawn from the centre of its base, a curve, the angle of which would be ninety degrees. But what has been said, with respect to an inclination of the tube necessary to make the drop pass through it... depends upon the proportion between the motion of the tube, and the motion of the drop; and, in proportion as the motion of the drop is greater than that of the tube, the less the tube must be inclined: so that, if the motion of the drop be supposed to be infinite, no inclination at all of the tube would be necessary... In order to apply this theory to the aberration of the fixed stars, we must substitute for the drops of water, uniting into a thread, the rays of light that come from those stars; and, for the tube, which we have supposed to be first at rest, and then in motion, that of the telescope used to determine the position of the stars, which is carried round with the Earth, in its revolution about the Sun; and we must suppose, that the velocity of the ray of light, having a finite relation to the velocity of the Earth's motion, the tube ought to change its inclination, in proportion as that motion changes its direction; whence it follows, that each star must have a series of different positions; or, which is the same thing, an apparent motion in the heavens, which causes it to describe, in the space of a year, ellipses more or less elongated according to its position. From the calculations of this gentleman it follows, that the velocity of light, as fixed by the aberrations of the stars, is the fame with what M Roëmer supposed it to be, and exactly quadrates with the retardation of the eclipses of the first satellite of Jupiter. A new proof of the truth of his hypothesis, if any new proof had been necessary."