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K : required P B, the height through whicha falling body would acquire the projectilevelocity, or the velocity at the point B.Then by the known properties of theparabola, draw K G perpendicular andB G horizontal, intersecting in G. MakeB E = 5^, and draw E N perpendicular,

intersecting B T in N. Join B K, anddraw B M perpendicular to B K, and withthe centre, M, in the line B M describea circle through B and N, intersecting I Bcontinued in P. BP is the height throughwhich a falling body will acquire the pro-jectile velocity. Bisect P B in A, and withthe centre, A, describe the circle through Pand B, intersecting B T in H. Through Hdraw VL horizontal, intersecting P B in L.Make H V = H L, V is the vertex. FromV draw V O perpendicular tb V L andthrough H draw P F, intersecting V O in F;

cable to the matter in question; but the author has notbeen able to come to the same conclusions in respect tosome of them; which may arise from his not understand-ing their precise meaning.