Algebra followed, and Father Lama was still my guide: when I made some progress, I perused Father Reynaud's Science of Calculation, and then his Analysis Demonstrated; but I never went far enough thoroughly to understand the application of algebra to geometry.

I was not pleased with this method of performing operations by rule without knowing what I was about: resolving geometrical problems by the help of equations seemed like playing a tune by turning round a handle.

The first time I found by calculation that the square of a binocular figure was composed of the square of each of its parts, and double the product of one by the other; though convinced that my multiplication was right, I could not be satisfied till I had made and examined the figure: not but I admire algebra when applied to abstract quantities, but when used to demonstrate dimensions, I wished to see the operation, and unless explained by lines, could not rightly comprehend it.
After this came Latin: it was my most painful study, and in which I never made great progress.

I began by Port-Royal's Rudiments, but without success; I lost myself in a crowd of rules; and in studying the last forgot all that preceded it.

A study of words is not calculated for a man without memory, and it was principally an endeavor to make my memory more retentive, that urged me obstinately to persist in this study, which at length I was obliged to relinquish.