PLATE I. 
Driving - screw, electrical control, and slow motion of the Cape 
Town 24-inch Refractor. 
a, Driving-screw. 
b, Detector fingers of electrical control. 
c, Hlectric motor for extra slow motion. 
d, Relays. - 
e, Hand commutator, by which either the old or new form of 
slow motion is controlled. 
