An' about this engine--Jim--ain't you got ne'er a pal as can use a soldering iron?
Seems to me that's about all the little bounder wants doing to it." "That's what Father said," Bobbie explained eagerly.

"What's that for ?" She pointed to a little brass wheel that he had turned as he spoke.
"That's the injector." "In--what ?" "Injector to fill up the boiler." "Oh," said Bobbie, mentally registering the fact to tell the others; "that IS interesting." "This 'ere's the automatic brake," Bill went on, flattered by her enthusiasm.

"You just move this 'ere little handle--do it with one finger, you can--and the train jolly soon stops.

That's what they call the Power of Science in the newspapers." He showed her two little dials, like clock faces, and told her how one showed how much steam was going, and the other showed if the brake was working properly.
By the time she had seen him shut off steam with a big shining steel handle, Bobbie knew more about the inside working of an engine than she had ever thought there was to know, and Jim had promised that his second cousin's wife's brother should solder the toy engine, or Jim would know the reason why.

Besides all the knowledge she had gained Bobbie felt that she and Bill and Jim were now friends for life, and that they had wholly and forever forgiven her for stumbling uninvited among the sacred coals of their tender.
At Stacklepoole Junction she parted from them with warm expressions of mutual regard.