All listened, as the young miner was doing.

His ears, which were very sharp, had caught a dull sound, like a distant murmur.

His companions were not long in hearing it themselves.

It was above their heads, a sort of rolling sound, in which though it was so feeble, the successive CRESCENDO and DIMINUENDO could be distinctly heard.
All four stood for some minutes, their ears on the stretch, without uttering a word.

All at once Simon Ford exclaimed, "Well, I declare! Are trucks already running on the rails of New Aberfoyle ?" "Father," replied Harry, "it sounds to me just like the noise made by waves rolling on the sea shore." "We can't be under the sea though!" cried the old overman.
"No," said the engineer, "but it is not impossible that we should be under Loch Katrine." "The roof cannot have much thickness just here, if the noise of the water is perceptible." "Very little indeed," answered James Starr, "and that is the reason this cavern is so huge." "You must be right, Mr.Starr," said Harry.
"Besides, the weather is so bad outside," resumed Starr, "that the waters of the loch must be as rough as those of the Firth of Forth." "Well! what does it matter after all ?" returned Simon Ford; "the seam won't be any the worse because it is under a loch.