Sentence:  To have a competent knowledge of what has been recited, besides a quick and discerning eye, are the proper accomplishments by which a <WSD>Corrector</WSD> may raise his own and his Master's credit: for it is a maxim with Booksellers, to give the first edition of a work to be done by such Printers whom they know to be either able <WSD>Correctors</WSD> themselves, or that employ fit persons, though not of Universal learning, and who know the fundamentals of every Art and Science that may fall under their examination. 
Meaning of the word marked with <WSD> tags:  A proofreader.