Various causes--how detected--procedure--heating, of connections; of brushes, commutator and armature--excessive heating--ventilated commutator--self-oiling bearing--some causes of hot bearing--effect of hot bearings--points relating to hot bearings--operation above rated voltage and below normal speed--forced system of lubrication--heating of field magnets--causes of eddy currents in pole pieces--detection of moisture in field coils--indication of short circuits in field coils. OPERATION OF MOTORS 663 to 696 Before starting a motor--starting a motor--various starting resistances--starting boxes--speed regulators--Cutler Hammer starter--time required to start motor--how to start--sliding contact starters--series motors on battery circuits--starting a shunt motor--multiple switch starters--effect of reverse voltage--rheostat with no voltage and overload release--failure to start--starting panel--Cutler Hammer starting rheostats--Allen Bradley automatic starter--Monitor starter with relay for push button control--a remote control of shunt motors--regulation of motor speed; various methods--Monitor printing press controller--speed regulation of series motor, by short circuiting sections of the field winding--varying the speed of shunt and compound motors--Cutler Hammer multiple switch starter--regulation by armature resistance--Compound starter--regulation by shunt field resistance--Holzer Cabot instructions for shunt wound motor--Reliance adjustable speed motor--Cutler Hammer reversible starter--combined armature and shunt field control--selection of starters and regulators--Watson commutators--organ blower speed regulator--General Electric controller--speed regulation of traction motors--controller of the Rauch and Lang electric vehicles--two motor regulation--controller connection diagrams--stopping a motor. CHAPTER XXVI GALVANOMETERS If a compass needle be allowed to come to rest in its natural position, and a current of electricity be passed through a wire just over it from north to south, the north seeking end of the needle will be deflected toward the east. If the wire be placed under the needle and the current continued from north to south the needle will be deflected toward the west. Again, if the current be passed from north to south over the needle, and back from south to north under the needle, as shown in fig. 504, the magnetic effect will be doubled, and the needle deflected proportionately. Upon these phenomena depend the working of galvanometers.