Sentence:  A Power that hath neither the Signs + or - before it, is look'd upon as Affirmative, and if it be preceded by a Number that contains the Root ſought and its <WSD>Exponent</WSD> may be commenſured by the <WSD>Exponent</WSD> of the Root; namely for the Square Root by 2, for the Cube by 3, &c. it will contain the Root ſought. 
Meaning of the word marked with <WSD> tags:  The degree to which the root of a radicand is found, for example, the 2 in \sqrt[2]r=b.