A locomotive is, next to a marine engine, the most sensitive thing man ever made; and No. .007, besides being sensitive, was new. The red paint was hardly dry on his spotless bumper-bar, his headlight shone like a fireman’s helmet, and his cab might have been a hard-wood-finish parlour. They had run him into the round-house after his trial—he had said good-bye to his best friend in the shops, the overhead travelling-crane—the big world was just outside; and the other locos were taking stock of him.