Abstract: Apparatus for monitoring the working stroke of a hydraulic ram 1 includes an indicator 3 having a housing 24 containing a tubular measuring chamber 25 connected to the hydraulic ram by a hydraulic line 2. The tubular measuring chamber is transparent on at least one side for the observation of the level of hydraulic fluid contained therein. The lower end of the tubular measuring chamber is connected to the hydraulic line leading to the hydraulic ram. The upper end of the tubular measuring chamber is closed by an air-permeable but dust-impermeable member 28.

Abstract: Apparatus for controlling the cutting horizon of a mineral winning plough comprises means for pivoting the guide along which the plough moves. The guide is fixed to the face side of the conveyor, and said means acts on the goaf side of the conveyor. Said means comprises a plurality of control devices, each of which has an upstanding plate fixed to the goaf side of the conveyor, an abutment member pivotally connected to the base of the upstanding plate, and an actuator arranged between the abutment member and the upstanding plate. The actuators are effective to pivot the conveyor relative to the abutment members. Each actuator comprises a hydraulic ram and a toggle linkage which magnifies the working stroke of the ram.