«L.C. forgot that "the Snark" is a tragedy and [should] on no account be made jovial.»

Letter by C.L. Dodgson (aka Lewis Carroll) to Henry Holiday. The two lines at the bottom are by Henry Holiday.

Source: www.pbagalleries.com/images/lot/1859/185970_0.jpg in www.pbagalleries.com/view-auctions/catalog/id/384/lot/119222/Original-drawing-by-Lewis-Carroll-in-illustration-of-The-Hunting-of-the-Snark-and-an-autograph-letter-from-him-to-the-book-s-illustrator-critiquing-his-designs-bound-into-a-copy-of-the-book

"... The letter, dated Jan. 4, 1876, highlights Carroll’s and Holiday’s different artistic vision for the book, and critiques Holiday’s illustrations for the work both generally and in particular ..."

Snapshot 2016-05-26
Processed (GIMP): high pass filtering and contrast enhancement

The note is:
«L.C. forgot that "the Snark" is a tragedy and [should]
on no account be made jovial. h.h.»