Ferguson leaves Edinburgh for London.—It is now not certainly known what made Ferguson resolve to leave Edinburgh. He would, no doubt, see many obstacles in the way to his attaining success in it. On looking around him he could not fail to observe that its trade was in a very depressed state; that there was then a scarcity of the “circulating medium;” that an apathy had settled down on its inhabitants; and that there was a consequent want of enterprise—a state of things, he would find, that had arisen since the Union, owing, in a great measure, to the large numbers of the nobility and gentry abandoning it for London. In short, Edinburgh, between the date of the Union, in 1707, and the year 1750, passed through one of the most depressed periods of its history—a period which has been designated “the dark age of Edinburgh.” It is therefore evident that Edinburgh, in 1743, was not the place to give full scope to Ferguson's genius, where he could expect to have success in his self-taught business of limning, or as an occasional writer on his favourite science of astronomy. We may also add, that Ferguson, about a year previous to his leaving Edinburgh, had set afloat in the London literary market there, two speculations—viz. “The Astronomical Rotula,” and an Astronomical Card-Dial. Of the success of the latter publication, nothing now is known; but the former—the Rotula—was successful.