Though he continued to follow this profession for about twenty-six years, be seems never to have given his mind to it ; and indeed, after baying been two years in Edinburgh, he returned to the country with a supply of drugs with the intention of practisiug medicine, but soon found himself to be totally unqualified for his new occupation. He then went to huserness, where he remained about three months. While there he drew an Astronomical Rotula, for exhibiting the eclipses of the sun and moon, which he transmitted to professor Maclaurin at Edinburgh, who was highly pleased with it. He now returned to Ediuburgh, and the Professor had the 'Rohde' engraved, and it ran through several impressions, till, by the change of the style in 1753, it became useless. While at Edinburgh he made a wooden orrery, and•delivercd a lecture on it before the mathematical class.
In 1743 he resolved to go to Loudon, where he coutinued his pro fession of drawing portraits, but devoted his leisure to astronomical pursuits.
In 1717 lie published his first work, ' A Dissertation on the Phe nomena of the Harvest Moon,' having been previously latroduocd at one of the sittings of the Royal Society by Mr. Folkee the president.
In 1718 he read lectures on the eclipse of the sun which happened in that year. From this period he began, under the patronage of the Priuce of Wales (afterwards George 111.), to deliver lectures on astronomy and mechanics ; they were numerously and fashionably attended, and he now relinquished his former profession altogether. From this time to the end of his life be continued his lectures, and wrote emeriti works on astronomy and mechanics.
Soon after the accession of George Ill, a pension of 501. a year wse granted him ont of the privy purse. In 1763 he was elected a Fellow if the Royal Society, and in 1770 was chosen a member of the American Philosophical Society.
He died in 1770, aged sixty-six, leaving an only eon, to whom he bequeathed a considerable sum acquired by his lectures and his cantinas.
Ferguson has contributed more then perhaps any other man in this country to the extension of physical science among all classes of society, but especially among that largest class whose circumstances preclude them from a regular course of scientific instruction. Perspi cuity in the selection and arrangement of his facts, and in the display of the truths deduced from them, was his cherecteristie both as a lecturer and a writer.
The following are his principal works Astronomy explained upon Sir Isaac Newton's Principles, and made easy to those who have not studied Mathematics,' Ito, 1756. There have been many editions of this work; one by Dr. (now Sir David) Brewster, 2 vols. 8vo, 1811, containing the new discoveries since the time of Ferguson. ' Lectures on Subjects In Mechanics, Hydrostatics, Pneuwatibs, and Optics, with the Use of the Globes, the Art of Dialling, and the Calculation of the Mean Times of New and Full Moons and Eclipses,' 8vo, 1760; 4to, 1704. An edition of this work by Dr. Brewster was published in 1805, and another in 1806. ' An Easy Introduction to Astronomy for Young Gentlemen and Ladies,' 1769. ' Introduction to Electricity,' 8vo, 1770. 'The Art of Drawing in Perspective made easy to those who have no previous knowledge of Mathematics,' 8ro,1775 : this was his last work. Besides other works not mentioned here, he contributed several papers to the 'Philosophical Transactions.' (Life by himself, prefixed to his 'Select Mechanical Exercises;' Nichols's Anecdotes; Cnok, Pursuit of Knowledge under Difficulties, vol. 1.)