The Sketchbook of the Week #6 is from Conrad Martens.
(click the underlined title next to the book icon to link to a interactive book.
Sketchbooks I & III:
Conrad Martens accompanied Charles Darwin (who’s now famous ”tree of life” note is the drawing of the day), aboard the HMS Beagle. Hired by the ship’s captain to visually document the voyage through his sketches, Martens and Darwin began a close friendship that lasted both their lifetimes.
To learn more: http://en.wikipedia.org/wiki/Conrad_Martens