Herschel the elder, having greatly improved the telescope, began to observe with special attention a class of remarkable phenomena in the starry world hitherto unstudied, viz.: milky spots in various stages of diffusion. The nature of these appearances soon cleared itself up thus far, that generally they were found to be starry worlds, separated from ours by inconceivable distances, and in that way concealing at first their real nature. The whitish gleam was the mask conferred by the enormity of their remotion. This being so, it might have been supposed that, as was the faintness of these cloudy spots or _nebulæ_, such was the distance. But _that_ did not follow: for in the treasury of nature it turned out that there were other resources for modifying the powers of distance, for muffling and unmuffling the voice of stars. Suppose a world at the distance _x_, which distance is so great as to make the manifestation of that world weak, milky, nebular. Now let the secret power that wields these awful orbs, push this world back to a double distance! _that_ should naturally make it paler and more dilute than ever: and yet by _compression_, by deeper centralization, this effect shall be defeated; by forcing into far closer neighborhood the stars which compose this world, again it shall gleam out brighter when at 2_x_ than when at _x_. At this point of compression, let the great moulding power a second time push it back; and a second time it will grow faint. But once more let this world be tortured into closer compression, again let the screw be put upon it, and once again it shall shake off the oppression of distance as the dew-drops are shaken from a lion's mane. And thus in fact the mysterious architect plays at hide-and-seek with his worlds. 'I will hide it,' he says, 'and it shall be found again by man; I will withdraw it into distances that shall seem fabulous, and again it shall apparel itself in glorious light; a third time I will plunge it into aboriginal darkness, and upon the vision of man a third time it shall rise with a new epiphany.'