Sentence:  If a Parallelogram be divided into four leſſer ones, by two Lines interſecting each other; and one of theſe Parallelograms be retrench'd, or taken away; the other three will make a <WSD>"Gnomon</WSD>", ordinarily call'd a "Square". 
Meaning of the word marked with <WSD> tags:  A plane figure formed by removing a parallelogram from a corner of a larger parallelogram.