John Gordon (1700–1778), a former Philadelphian now living near Princeton, N.J., managed to combine the trade of a bricklayer with the teaching of surveying and other mathematical arts.7 In the spring of 1757 he announced his intention of publishing by subscription a set of tables to assist “Mariners, Merchants, and Surveyors” in their calculations. As a matter of timely importance he added that his work would also “be of great use to all Military Gentlemen in any Part of the World, in forming their Marches, or other important Schemes or Designs of an Army.” To this announcement in the newspapers and to the prefatory statement in the book itself, when it appeared the next year, he appended a series of testimonials as to the utility of his tables.8 The first three of these endorsements are printed here, comprising the comments of two New Jersey surveyors and of one from Pennsylvania, and, perhaps inevitably, one by Franklin. It will be noticed, however, that the last of these wisely offered no personal judgment on the value of Gordon’s tables—a matter probably beyond Franklin’s mathematical competence—but merely endorsed the endorser just before him.