Page:Bentley- Trent's Last Case (Nelson, nd).djvu/187

Rh at it again. You saw nothing odd about it before. Do you see anything now?'

Mr. Cupples peered again. 'How curious!' he said. 'Yes, there are two large grey finger-marks on the bowl. They were not there before.'

'I am Hawkshaw the detective,' observed Trent. 'Would it interest you to hear a short lecture on the subject of glass finger-bowls? When you take one up with your hand you leave traces upon it, usually practically invisible, which may remain for days or months. You leave the marks of your fingers. The human hand, even when quite clean, is never quite dry, and sometimes–in moments of great anxiety, for instance, Cupples–it is very moist. It leaves a mark on any cold smooth surface it may touch. That bowl was moved by somebody with a rather moist hand quite lately.' He sprinkled the powder again. 'Here on the other side, you see, is the thumb-mark–very good impressions all of them.' He spoke without raising his voice, but Mr. Cupples could perceive that he was ablaze with excitement as he stared at the faint grey marks. 'This one should be the index finger. I need