Jonathan Dakin worked as a mathematical balance-maker "at the Sign of the Hand & Beam, opposite to Dr. Colman's Meeting House" where he made a variety of scale beams in 1745.[31] An interesting advertisement by Rowland Houghton appeared in the January 17-24, 1737, issue of the _Boston Gazette_. Houghton announced that he had "lately improv'd on his new Theodolite, by which the Art of Surveying is rendered more plain & easy than heretofore." Houghton was active in the political scene in Boston, as evidenced by the fact that in various issues of the _Boston Gazette_ for January and February 1739 he is listed variously as "Commissioner," "Proprietors' Clerk" and as "Collector." Isaac Greenwood, Jr. (1730-1803), was born at Cambridge, where he married Mary I'ams in 1757. He maintained a shop where he combined the business of mathematical instrument maker and ivory turner, and also imported hardware. After the Revolution, he engaged in dentistry, specializing in making artificial teeth and in the manufacture of "umbrilloes." Paul Revere apparently did printing for him on five different occasions between 1762 and 1774, and in about 1771 engraved his trade card, which read: ISAAC GREENWOOD, Ivory Turner Next door to Doctor John Clark's at the North End Boston. Turns all sorts of work in Ivory, Silver, Brass, Iron, Horn, Wood, etc. Such as Billiard Balls, Tea Boards, Scallop^d and Plain Salvers, Decanters ...[32] Isaac's father, Isaac Greenwood, Sr., was "Professor of Mathematicks and Natural and Experimental Philosophy" at Harvard. In the _Boston Gazette_ for February 19-26, 1728, there appeared the following notice of his installation: On the 13th of this Month at Ten in the Morning, The Honorable & Reverend Overseers of the College at Cambridge, met the Corporation in the College Hall, to Inaugurate Mr. Isaac Greenwood into the Office of Professor of the Mathematicks, and Natural and Experimental Philosophy, lately founded by that great and living Benefactor to this Society, Mr. Thomas Hollis of London Merchant. The Rev. President being detain'd by illness, Mr. Flint the Senior Fellow perform'd the part of Moderator, began with Prayer, and then Pronounc'd a Latin Oration proper to the Occasion: Mr. Wiggleworth Divinity Professor, read the Founders Instructions. Mr. Greenwood took the Oaths and made the Declarations required in them: and pronounc'd a Latin Oration. The Rev. Mr. Appleton Pray'd: and Singing part of the 104 Psalm concluded the Solemnity. After which the Overseers & Corporation repair'd to the Library; till the Publick Dinner in the Hall was ready, where all the Gentlemen Spectators of the Solemnity were hansomely Entertained. Greenwood continued to teach privately for a decade. In various issues of _The Boston Gazette_ of 1738 and 1739 he featured an advertisement, the text of which always stated: