24 TRANS. OF THE ACAD. OF SCIENCE. 
Mr. James B. Eads submitted for the consideration of the 
Academy the following explanation of the mechanical principles 
of the Rotoscope: 
“The causes producing this Meld phenomenon are four 
well settled principles in the science of Mechanics, viz: Gravita- 
tion, friction, the tendency of jialter in motion to move in right ; 
lines, and, as the result of the latter, centrifugal for 3 
*« There are several Peas eatin’ a the machine, al the same 
causes act in all to produce the 
“The instrument in the Reais: of the Academy consists of 
a metal ring, on opposite sides of which are two lugs or ears; by 
one of these the ring is supported upon the pointed end of a ver- 
tical rod, having a heavy base to steady it; and across this ring, 
and supported by a pivot at each lug, is a shaft or spindle, having 
on its centre a heavy fly-wheel, just large enough to clear the 4 
ring. The spindle has a conical socket at each end, into which ; 
he pivots enter for its support. The position of the ring is hori- = 
zontal, and, of course, that of the spindle is the same. When 
Byte is made to revolve Bach and the ring is rested by its 
e ring begins to revolve also slowly 
verti see ah i hit the fly- 
ft, and apparently setting the laws f gravitatio n at 
As the velocity of the i decreases, the revolutions 
ome more rapid, until it gradually sinks below the 
mn, and finally £ falls off the vertical rod around 
‘the ring are caused bythe forte of grave 
ae supporting tl he fly-wh seaman 
