It is a memorable and a curious speculation to reflect, upon how slight grounds the doctrine of "thousands and thousands of suns, multiplied without end, and ranged all around us, at immense distances from each other, and attended by ten thousand times ten thousand worlds," mentioned in the beginning of this Essay, is built. It may be all true. But, true or false, it cannot be without its use to us, carefully to survey the road upon which we are advancing, the pier which human enterprise has dared to throw out into the vast ocean of Cimmerian darkness. We have constructed a pyramid, which throws into unspeakable contempt the vestiges of ancient Egyptian industry: but it stands upon its apex; it trembles with every breeze; and momentarily threatens to overwhelm in its ruins the fearless undertakers that have set it up. It gives us a mighty and sublime idea of the nature of man, to think with what composure and confidence a succession of persons of the greatest genius have launched themselves in illimitable space, with what invincible industry they have proceeded, wasting the midnight oil, racking their faculties, and almost wearing their organs to dust, in measuring the distance of Sirius and the other fixed stars, the velocity of light, and "the myriads of intelligent beings formed for endless progression in perfection and felicity," that people the numberless worlds of which they discourse. The illustrious names of Copernicus, Galileo, Gassendi, Kepler, Halley and Newton impress us with awe; and, if the astronomy they have opened before us is a romance, it is at least a romance more seriously and perseveringly handled than any other in the annals of literature. A vulgar and a plain man would unavoidably ask the astronomers, How came you so familiarly acquainted with the magnitude and qualities of the heavenly bodies, a great portion of which, by your own account, are millions of millions of miles removed from us? But, I believe, it is not the fashion of the present day to start so rude a question. I have just turned over an article on Astronomy in the Encyclopaedia Londinensis, consisting of one hundred and thirty-three very closely printed quarto pages, and in no corner of this article is any evidence so much as hinted at. Is it not enough? Newton and his compeers have said it.