Sentence:  In the following odd multiples above the ſeptuple arc, the mean arc may be greater than three quadrants: Thus, for inſtance, in the caſe of the <WSD>noncuple</WSD> arc, in which the three equidifferent<!-- hyphenated as “equi-different” across a line break in the source --> arcs are the quintuple, ſeptuple, and <WSD>noncuple</WSD> arcs, ‛tis evident the greateſt magnitude of the ſeptuple, or mean, arc, or that which it has when the <WSD>noncuple</WSD> arc is equal to a whole circle, is ⁷⁄₉, or ²⁸⁄₃₆, of the whole circumference, which is greater than ²⁷⁄₃₆ or ¾ of the whole circumference, or three quadrants; and ſince this is true in the <WSD>noncuple</WSD> arc, it follows a "fortiori"<!-- unitalicised ‘a' sic --> that it will be true in all higher multiples. 
Meaning of the word marked with <WSD> tags:  Divided into nine equal segments.