Establish the meaning of these without question, and we have principia from which we may deduce creeds and systems, the usefulness of which cannot be exaggerated, especially in an age of agnosticism.

I went through Euclid (as far as usually read), Wood's Algebra, Wood's Mechanics, Vince's Hydrostatics, Wood's Optics, Trigonometry (in a geometrical treatise and also in Woodhouse's algebraical form), Fluxions to a good extent, Newton's Principia to the end of the 9th section.

on the Differential Calculus, which it appears I wrote then: one on the Figure of the Earth written about August 15th; one on Tides, Sept. 25th; one on Newton's Principia with algebraical additions, Nov. 1st