A suggestion of motion may be obtained by exhibiting a number of persons engaged in similar actions, but shown in a consecutive series of stages thereof. This plan is admirably worked out by Watteau in his Embarkation for Cythera.[a] A line of couples commences at the right of the picture, proceeds towards the left, and then descends a slope to the place of embarkation. The first couple are sitting and conversing, the next are in the act of rising, and the third have just risen and are about to follow the other couples already walking, the whole device being most effective. A similar kind of illusion is caused by Rubens in his Diana and Nymphs pursued by Satyrs.[b] On the extreme right of the picture some of the figures are stationary; then come a few who are struggling, and finally some running nymphs and satyrs, a perfect progression of events being suggested. [a] In the Louvre, and repeated with variations at Berlin. [b] The Prado, Madrid. See Plate 27. Illusion of motion is more easily obtained with animals than with human figures, providing they are fairly large, because of the greater number of their feet and the consequent wider variation between the apparent and the real movements. It is exceedingly difficult to produce a suggestion of motion with a single animal represented in a natural attitude, but the painter is only concerned with what appears to be natural or probable, and not with what is actually so. We have only a general idea of the action of a horse in nature from what we see, and consequently in design this action must be generalized irrespective of natural possibilities. Some artists combine parts of different actions as exhibited in a series of photographs in order to represent a moment of action as it is generalized to the eye, but this is only serviceable where the presumed action of the animal is one of a series of similar events, as in walking or trotting. It would not answer in the case of an isolated action, as jumping or rearing, because such actions vary with the circumstances surrounding them, as the height of the jump or the cause of the rearing. In these events therefore the artist may exaggerate to a great extent without appearing to present impossible movements. In fact nearly all good pictures of one or two horses in action are strong exaggerations of nature, but this hardly affects their æsthetic worth because the action is not recognized as abnormal or impossible. The finest painting of horses in action known to us, is Regnault's Automedon with the Horses of Achilles,[a] where the animals exhibit spirit and movement far above experience, but even if we did not know that they are presumed to be immortal, we should only regard the action as exceptional, for it does not appear to be impossible. [a] Boston Museum, U. S. A. See Plate 28.