‘No, no, my dear Watson, not all—by no means all. I would suggest, for example, that a presentation to a doctor is more likely to come from a hospital than from a hunt, and that when the initials ‘C.C.’ are placed before that hospital the words ‘Charing Cross’ very naturally suggest themselves.’

‘You may be right.’

‘The probability lies in that direction. And if we take this as a working hypothesis we have a fresh basis from which to start our construction of this unknown visitor.’

‘Well, then, supposing that ‘C.C.H.’ does stand for ‘Charing Cross Hospital,’ what further inferences may we draw?’

Do none suggest themselves? You know my methods. Apply them!’

‘I can only think of the obvious conclusion that the man has practised in town before going to the country.’

‘I think that we might venture a little farther than this. Look at it in this light. On what occasion would it be most probable that such a presentation would be made? When would his friends unite to give him a pledge of their good will? Obviously at the moment when Dr. Mortimer withdrew from the service of the hospital in order to start in practice for himself. We know there has been a presentation. We believe there has been a change from a town hospital to a country practice. Is it, then, stretching our inference too far to say that the presentation was on the occasion of the change?’