Once more the engine labored; nor was it until Barry had answered its gasping plea by a shift to second gear that it strengthened again.

The grade was growing heavier; once Barry turned his head and stared with the knowledge that far beneath him a few tiny buildings dotted what seemed to be a space of ground as level as a floor.

Dominion! And he had barely passed outside its environs! He settled more firmly in his seat and gripped hard at the steering wheel.

The turns had become shorter; more, Barry found himself righting the machine with sudden jerks as the car rounded the short curves where the front wheels seemed to hang momentarily above oblivion, as the chasms stretched away to seemingly bottomless depths beneath.

Gradually, the severity of the grade had increased to ten, to twelve and in short pitches to even eighteen and twenty per cent! For a time the machine sang along in second, bucking the raises with almost human persistence, finally, however, to gasp and break in the smooth monotony of the exhaust, to miss, to strain and struggle vainly, then to thunder on once more, as Houston pressed the gears into low and began to watch the motormeter with anxious eyes.