a large iron trough, and when I came to examine it I could see a crust of metallic deposit all over it. I had stooped and was scraping at this to see exactly what it was when I heard a muttered exclamation in German and saw the cadaverous face of the colonel looking down at me.
“ ‘What are you doing there?’ he asked.
“I felt angry at having been tricked by so elaborate a story as that which he had told me. ‘I was admiring your fuller’s-earth,’ said I; ‘I think that I should be better able to advise you as to your machine if I knew what the exact purpose was for which it was used.’
“The instant that I uttered the words I regretted the rashness of my speech. His face set hard, and a baleful light sprang up in his grey eyes.
“ ‘Very well,’ said he, ‘you shall know all about the machine.’ He took a step backward, slammed the little door, and turned the key in the lock. I rushed towards it and pulled at the handle, but it was quite secure, and did not give in the least to my kicks and shoves. ‘Hullo!’ I yelled. ‘Hullo! Colonel! Let me out!’