" There was a gasp from the audience, and one could almost see the mental cog wheels of sixty girls going furiously to work.

In the center of the track, between the heavy steel rails, are two cog rails, of great strength.

The engine and the cars have each independent cog brakes of almost unlimited power.

But let one little cog slip and the whole plan falls to bits, and we are alone in the old untamed Moghreb, as remote from Europe as any mediaeval adventurer.