"I stood last summer on the summit of Tor-Achilty [a pyramidal hill about six miles from Conon side], and occupied, when there, the centre of a wide circle, about fifty miles in diameter. I can still call up its rough-edged sea of hills, with the clear blue firmament arching over, and the slant rays of the setting sun gleaming athwart. Yes, over that circular field, fifty miles across, the firmament closed all around at the horizon, as a watch-glass closes round the dial-plate of the watch. Sky and earth seemed co-extensive; and yet how incalculably vast their difference of area! Thousands of systems seemed but commensurate, to the eye, with a small district of earth fifty miles each way. But capacious as the human imagination has been deemed, can it conceive of an area of wider field? Mine cannot. My mind cannot take in more at a glance, if I may so speak, than is taken in by the eye. I cannot conceive of a wider area than that which the sight commands from the summit of a lofty eminence. I can pass in imagination through many such areas. I can add field to field _ad infinitum_; and thus conceive of infinite space, by conceiving of a space which can be infinitely added to; but all of space that I can take in at one process, is an area commensurate with that embraced at a glance by the eye. How, then, have I my conception of the earth as a whole--of the solar system as a whole--nay, of many systems as a whole? Just as I have my conceptions of a school-globe or of an Orrery--by diminution. It is through the diminution induced by distance that the sidereal heavens only co-extend, as seen from the top of Tor-Achilty, with a portion of the counties of Ross and Inverness. The apparent area is the same, but the colouring is different. Our ideas of greatness, then, are much less dependent on actual area than on what painters term aerial perspective. The dimness of distance, and the diminution of parts, are essential to right conceptions of great magnitude.