The class of phenomena we are about to describe are those produced by the interposition of celestial objects; for we know well that inasmuch as many of the heavenly bodies are constantly in motion, it follows that the direction of lines drawn from one to another will vary from time to time; and it must occasionally happen that three will come into the same line. “ When one of the extremes of the series of 3 bodies, which thus assume a common direction, is the Sun, the intermediate body deprives the other body, either wholly or partially, of the light which it habitually receives. ”When one of the extremes is the Earth, the intermediate body intercepts, wholly or partially, the other extreme body from the view of observers situate at places on the Earth which are in the common line of direction, and the intermediate body is seen to pass over the other extreme body, as it enters upon or leaves the common line of direction, and the intermediate body is seen to pass over the other extreme body, as it enters upon or leaves the common line of direction. The phenomena resulting from such contingencies of position and direction are variously denominated ‘Eclipses’ ‘Transits’ and ‘Occultations’ according to the relative apparent magnitudes of the interposing and obscured bodies, and according to the circumstances which attend them.“ We shall proceed to consider the several phenomena in detail, beginning with Eclipses.