This vast augmentation of telescopic compass was due as much to the increased tranquillity as to the increased transparency of the air. The stars hardly seemed to twinkle at all. Their rays, instead of being broken and scattered by continual changes of refractive power in the atmospheric layers through which their path lay, travelled with relatively little disturbance, and thus produced a far more vivid and concentrated impression upon the eye. Their images in the telescope, with a magnifying power of 150, showed no longer the “amorphous figures” seen at Edinburgh, but such minute, sharply-defined discs as gladden the eyes of an astronomer, and seem, in Professor Smyth’s phrase, to “provoke” (as the “cocked-hat” appearance surely baffles) “the application of a wire-micrometer” for the purposes of measurement.[10] The lustre of the milky way and zodiacal light at this elevated station was indescribable, and Jupiter shone with extraordinary splendor. Nevertheless, not even the most fugitive glimpse of any of his satellites was to be had without optical aid.[11] This was possibly attributable to the prevalent “dust-haze”, which must have caused a diffusion of light in the neighborhood of the planet more than sufficient to blot from sight such faint objects. The same cause completely neutralized the darkening of the sky usually attendant upon ascents into the more ethereal regions, and surrounded the sun with an intense glare of reflected light. For reasons presently to be explained, this circumstance alone would render the Peak of Teneriffe wholly unfit to be the site of a modern observatory. Within the last thirty years a remarkable change, long in preparation,[12] has conspicuously affected the methods and aims of astronomy; or, rather, beside the old astronomy—the astronomy of Laplace, of Bessel, of Airy, Adams, and Leverrier—has grown up a younger science, vigorous, inspiring, seductive, revolutionary, walking with hurried or halting footsteps along paths far removed from the staid courses of its predecessor. This new science concerns itself with the _nature_ of the heavenly bodies; the elder regarded exclusively their _movements_. The aim of the one is _description_, of the other _prediction_. This younger science inquires what sun, moon, stars, and nebulæ are made of, what stores of heat they possess, what changes are in progress within their substance, what vicissitudes they have undergone or are likely to undergo. The elder has attained its object when the theory of celestial motions shows no discrepancy with fact—when the calculus can be brought to agree perfectly with the telescope—when the coursers of the heavens come strictly up to time, and their observed places square to a hair’s-breadth with their predicted places.