Page:Collingwood - Life and Letters of Lewis Carroll.djvu/365

Rh A letter to the widow of an old college friend reveals the extraordinary sensitiveness of his nature:—

September 27th and 28th are marked in his Diary "with a white stone":—

Sept. 27th.—Dies notandus. Discovered rule for dividing a number by 9, by mere addition and subtraction. I felt sure there must be an analogous one for 11, and found it, and proved first rule by algebra, after working about nine hours!

''Sept. 28th. — Dies cretâ notandus''. I have actually superseded the rules discovered yesterday! My new rules require to ascertain the 9-remainder, and the 11-remainder, which