This is a Crookes railway tube, it is a mostly evacuated tube with electrodes on each end and a spinny wheel on a rail in between. When the electrodes are connected to a high voltage supply, electrons are launched off of the cathode with great speed and some collide with the little paddle wheel on thier way to the oppositely charged anode setting it spinning down the track. This device was invented in the 1880s by William Crookes during his investigations into the nature of electrons, without which of course this neat clip wouldn't be posted to youtube 120 years later.