We guard our secret very jealously, however, and if it once became known that we had hydraulic engineers coming to our little house, it would soon rouse inquiry, and then, if the facts came out, it would be goodbye to any chance of getting these fields and carrying out our plans. That is why I have made you promise me that you will not tell a human being that you are going to Eyford tonight. I hope that I make it all plain?’

“ ‘I quite follow you,’ said I. ‘The only point which I could not quite understand was what use you could make of a hydraulic press in excavating fuller’s-earth, which, as I understand, is dug out like gravel from a pit.’

“ ‘Ah!’ said he carelessly, ‘we have our own process. We compress the earth into bricks, so as to remove them without revealing what they are. But that is a mere detail. I have taken you fully into my confidence now, Mr. Hatherley, and I have shown you how I trust you.’ He rose as he spoke. ‘I shall expect you, then, at Eyford at 11:15.’