There are three hyperboles in this excerpt from "The £1,000,000 Bank-Note":
"They'll flock in droves". Here the word flock used as a verb means to gather together as a flock (word used to refer to a group of animals, specially birds). Therefore, the phrase is an hyperbole because it contrasts the idea of "a group of animals in a rush" to refer to "these rich Londoners" so as to cause a sense of exaggeration.
"I'm a made man forever". The use of the word "forever" here is used to add emphasis to the fact that the character will be a made man as long as he lives: everyone knows nothing lasts forever.
"In less than twenty-four hours London was abuzz!". Here the phrase "less than twenty-four hours" is employed to highlight how fast it took the rich Londoners to hear about the mine selling.
