Pleasure in riding and driving being partly due to the control we have over the horses, such enjoyment is a combination of active and passive. Even when we are only steering a boat the illusion is easily supported that we are to some extent responsible for its progress. Riding has other elements of attraction: besides the forward motion and lofty seat there is some peculiar enjoyment of each particular gait, the sensuously agreeable canter and the hard shake of the trot, which, so far as it can be pleasurable, furnishes an instance of more vehement enjoyment. Among artificial means of locomotion, those are most agreeable which afford a swift and yet smooth gliding or rocking motion. Souriau says in his Esthétique du Mouvement that the chief attraction of movement-plays lies in the overcoming of gravitation. But in that case, as I pointed out in my earlier work, downward movement would have no charm, since gravitation is there triumphant. The child’s first jump is, as we have seen, downward, and the downward rush of a sled fills us with exquisite delight. Souriau’s other supposition, that perhaps it is the exemption from friction, from the slight hindrances and detentions which commonly attend our movements, which accounts for our pleasure,[199] seems more probable. It is to be hoped that among the sports of the future, flying either in balloons or with flying machines will be included. Lilienthal, in recounting his experiences in these arts, assures us that gliding through the air in a slanting direction affords a new and delightful sensation. A long list of inventions, for the most part recreative, meet the demand for aids to active locomotion, notably appliances for rowing and the bicycle. Among ancient implements of this character I mention but two: stilts and snowshoes. Running on stilts is a favourite sport of children, both on account of the difficulties it presents and because of the elevation it affords. It was practised by both Greeks and Romans, and Pollux mentions a Spartan dance which was performed on stilts, probably the kind which is bound to the foot.[200] In speaking of the ethnological distribution of this custom Andree says that stilts are found all over the world. “In China they are very skilfully used, and are not unknown to Africa among many African tribes. The negro boys left of the Congo bind stilts to their ankles to appear taller. They are well known to the Malays and the inhabitants of the South Sea Islands. In Tahiti a limb of a tree is used, having a smaller branch projecting at about a metre from the ground, and in this fork the foot is placed. The beautifully carved stilts of the Marquise Islanders have attained a certain celebrity.”[201] The snowshoe, which has recently become popular once more, seems to be as ancient as the skate.[202]