d always an abyss under his feet！ We are on firm ground here； and need never be afraid of foundering。〃
〃I won't tease you； then； old Simon；〃 answered James Starr。 〃Far be it from me even in jest to depreciate the New Aberfoyle mine by an unjust parison！ I only meant to say one thing； and that is that we don't know where we are。〃
〃We are in the subsoil of the county of Stirling； Mr。 Starr；〃 replied Simon Ford； 〃and that I assert as if……〃
〃Listen！〃 said Harry； interrupting the old man。 All listened； as the young miner was doing。 His ears； which were very sharp； had caught a dull sound； like a distant murmur。 His panions 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 c