Because its wings meet the air obliquely, just as the surface of the kite does. And the twirling of the top, causing the oblique surfaces of its wings to strike the air, produces the equivalent effect of a wind from the earth blowing the top upwards.
"Children obey your parents in the Lord: for this is right."
844. Why does the flying-top return to the earth when its rotations are expended?
Because the reaction produced by its wings striking upon the air, is insufficient to counteract the attraction of gravitation.
Fig. 34.—FLYING-TOP.