It has already been described how the telescope can be moved by motors north or south and east or west at the rate of 45 degrees per minute. These motors are operated from small switchboards on each side of the south pier, the one at the west being seen in Figs. 2 and 3. The left-hand reversing switch moves the telescope east or west, the centre switch north or south and the right-hand switch revolves the dome east or west. In addition to these quick motions of the telescope for rapidly bringing it to the approximate position, much finer and slower motions are required for bringing the image exactly central and for guiding. These slow motions are also operated by electric motors actuated by two small aluminium switchboards attached by flexible cables to the top and bottom of the tube. These switchboards can be carried in the hands of the observer or rested on the observing ladder. Pressure on suitable buttons moves the telescope north or south, east or west at either one of two different speeds, a speed of one revolution in 36 hours for centering the image and a speed of one revolution in 30 days for guiding, correcting for slight irregularities due to air disturbance or other causes. Although these speeds may seem excessively slow, the motion of the image even with the monthly rate is at once evident on pressing the button and faster speeds would make accurate guiding difficult. In addition to the two quick and two slow motion motors there are two clamping motors and one for automatically rewinding the clock weight, seven in all. These with the three motors operating the dome are all continuous current motors which can be started and reversed more readily and have greater initial torque than alternating motors. Each motor is supplied with an automatic control, so that all that is necessary is to throw the switch or press the button to start or reverse. Current is supplied by a motor generator set on the ground floor. Method of Operation