1120.
Just as on a frozen river a man may run without moving his feet, so a car might be made that would slide by itself.
[Footnote: The drawings of carts by the side of this text have no direct connection with the problem as stated in words.—Compare No. 1448, l. 17.]
1121.
A definition as to why a man who slides on ice does not fall. [Footnote: An indistinct sketch accompanies the passage, in the original.]
On Flying machines (1122-1126).
1122.
Man when flying must stand free from the waist upwards so as to be able to balance himself as he does in a boat so that the centre of gravity in himself and in the machine may counterbalance each other, and be shifted as necessity demands for the changes of its centre of resistance.
1123.
Remember that your flying machine must imitate no other than the bat, because the web is what by its union gives the armour, or strength to the wings.