It was very agreeable to turn from Tom to Annie, and in a moment his air castle was built again, and throned on clouds of gold and purple.

I do not know what impossible things he imagined, or how far up in the clouds he would have gone, if the arrival of the train at the city had not interrupted his thoughts, and pitched him down upon the earth again.
Bobby was not one of that impracticable class of persons who do nothing but dream; for he felt that he had a mission to perform which dreaming could not accomplish.

However pleasant it may be to think of the great and brilliant things which one _will_ do, to one of Bobby's practical character it was even more pleasant to perform them.

We all dream great things, imagine great things; but he who stops there does not amount to much, and the world can well spare him, for he is nothing but a drone in the hive.

Bobby's fine imaginings were pretty sure to bring out a "now or never," which was the pledge of action, and the work was as good as done when he had said it.
Therefore, when the train arrived, Bobby did not stop to dream any longer.