Clouds and trees is drawn on the verso of a partial draft of the Ten o'clock Lecture, which dates from about February 1885. The draft relates to the passage:

'Let him judge a picture historically by the back of the canvass - after the manner of the orthodox Expert. Let him confine himself to inocuous statistics - Let him pick up, pedigrees vouched for by family seals and details behind the frame.' 1

This has nothing to do with the sketch, though it is relevant to research on a catalogue of Whistler's drawings!

Clouds and trees, Glasgow University Library

The drawing is catalogued in MacDonald 1995 (cat. rais.) [more] (cat. no. 995).