A description, with instructions for the use, of a newly invented surveying instrument, called the trigonometer : For the making and vending of which, the inventor hath obtained an exclusive right for twenty-one years, from the legislature of Pennsylvania. ... : The whole illustrated with cuts, and an elegant engraving of the instrument. / - Wall, George, (Printed by Zachariah Poulson, Junr. on the west side of Fourth-Street, near the University,, 1788)