you must farther make n. 4. as a to ½bb (DM to LN) so ¼c to a fourth (MQ to NR) which must be put from f to g. Lastly the quantity 〈 math 〉〈 math 〉 (which is = MO n. 2.) must be put backwards (because to be substracted) from g to H, which is the centre sought. In like manner by Baker's form, first 〈 math 〉〈 math 〉=BE is put from D to 1 even to the Ax. Secondly, for the quantity 〈 math 〉〈 math 〉 make, n. 4. as a to 〈 math 〉〈 math 〉 (LM to LS=CF n. 2.) so 〈 math 〉〈 math 〉 to a fourth (MT=AC n. 2. to SV) and this SV is further put (n. 3.) from 1 to 2. Thirdly, make in the same Fig. n. 4. for the quantity 〈 math 〉〈 math 〉, as a to 〈 math 〉〈 math 〉 (LM to MT) so 〈 math 〉〈 math 〉 to a fourth (LX to XZ) and this XZ is put back∣wads (n. 3.) from 2 to 3, which precisely coincides with the point g. Lastly the remaining quantity 〈 math 〉〈 math 〉 (=MO n. 2. and so by what we have said above, precisely coinciding with the interval g H) is put backwards from g to H the Centre sought.
[Hence it appears again that Baker's form is more laborious than ours; tho' both accurately agree, and hereafter, for the most part, we shall use them both together, tho in' the work it self, rather in Figures, than in that tedious process of words, which we have here for once made use of, that it might be as an Example for the following Constructions.]
Having therefore found by one or both ways the Center H, and thence described a circle thro' the vertex of the parabola A, the intersection N will give the perpendicular to the dia∣meter NO, the value of the quantity x sought.