1. In combination with a carriage and an elongated cable reach which supports the carriage with the carriage movable along said cable reach, means for propelling the carriage along said cable reach comprising motor means mounted on said carriage, sheave means also mounted on said carriage, said sheave means including at least one sheave rotatably mounted on said carriage drivingly connected to and adapted to be rotated under power by said motor means, and an elongated stationary line reach extending along and adjacent said cable reach, said line reach including a bend portion adjacent said carriage curving over a portion of and frictionally engaging said one sheave, powered rotation of said sheave by said motor means causing said sheave to advance along said line reach to propel the carriage on the cable reach.

3. In combination with a carriage and an elongated cable reach which supports the carriage with the carriage movable along said cable reach, adjustable means on the carriage for holding a load, and means for propelling the carriage together with such load along said carriage reach, the latter means comprising an elongated stationary line reach extending along and adjacent said cable reach, a sheave rotatably mounted on said carriage frictionally engaging a bend of said line reach, and disposed for rolling contact along said line reach with rotation of the sheave, and motor means also mounted on said carriage, drivingly connected to said sheave and operable to rotate the same under power, powered rotation of said sheave by said motor means causing said sheave to advance along said line reach to propel the carriage.

6. In a cable-logging system, the combination of an elongated aerial cable and a carriage mounted for travel back and forth along said cable, powered adjustable Means on the carriage for holding a load, and means for propelling the carriage together with such load along said cable, the latter means comprising an elongated stationary line extending along and adjacent said cable, a sheave assembly including a plurality of sheaves rotatably mounted on said carriage said stationary line extending in bends over said sheaves and the sheaves being disposed for rolling contact along said stationary line with rotation of the sheaves, said line passing into and out of said assembly of sheaves at regions disposed below the cable which regions together with the cable occupy substantially a vertical plane, and a reversible hydrualic motor also mounted on said carriage drivingly connected to said sheaves and operable to rotate the same under power.