I scanned the above page from the book,” Forty Illustrators and How They Work” by Ernest William Watson.
Wallace Morgan was a combat artist during WW1. These are quick visual notations that were made "on the spot". Nothing is more important than quick gesture drawing skills when you are being shot at. For an explanation of gesture drawing click here. These rough sketches have all the necessary information needed for the artist to flesh them out into complete illustrations, well behind the danger of the front lines.
Wallace Morgan circa 1918