Arthur Ransome Wiki

In Dick’s Pocket Book Dick notes birds he has seen and things he wants to remember, e.g. his mother’s birthday (illustrations, WH5).

In Winter Holiday Nancy wrote out the Morse alphabet … in Dick’s private pocket-book of scientific notes (WH5). After rescueing the sheep he pulled out his pocket book and scrawled (with frozen fingers) "Saw buzzards nest". (WH12). At the North Pole he digs in his pocket and shows Nancy the entry about the flag: (WH28) .

He turned hurriedly back, through sketches of the constellations, drawings of the Nansen sledge, the pages on which Nancy herself had drawn the semaphore alphabet for him, and the Morse code, until he came to the page for which he was looking. There, at the bottom of some mixed notes, he found what he wanteed, and held it out for her to see.
Flag on Beckfoot – start for Pole

In The Big Six Dick has the sketch of the bike tyre tracks in his pocket-book and later puts photographs of Coots in his pocket book .... to flatten them (BS14; note: spelt with and without a hyphen).

In Great Northern? it is called a note book (GN6); he sketches the mysterious Diver, and later shows it to Mr Jemmerling (GN9).