If we paint the phases of a riot, the crowd bustling with uplifted fists and the noisy onslaughts of cavalry are translated upon the canvas in sheaves of lines corresponding with all the conflicting forces, following the general laws of violence of the picture... These force-lines must encircle and involve the spectator so that he will in a manner be forced to struggle himself with the persons in the picture.

p. 8. - 'Les exposants au public', 1912