case may rest should be subjected to critical examination for it is an established fact that a photograph may be made as untruthful as it may be reliable.  Combination photographs change entirely the character of the initial negative and have been made for the past fifty years.  The earliest, simplest, and most harmless photographic deception is the printing of clouds into a bare sky.  But the retoucher with his pencil and etching tool to-day is very skilful.  A workman of ordinary skill can introduce a person taken in a studio into an open-air scene well blended and in complete harmony without a visible trace of falsity.

“I need say nothing of how one head can be put on another body in a picture, nor need I say what a double exposure will do.  There is almost no limit to the changes that may be wrought in form and feature.  It is possible to represent a person crossing Broadway or walking on Riverside Drive, places he may never have visited.  Thus a person charged with an offence may be able to prove an alibi by the aid of a skilfully prepared combination photograph.

“Where, then, can photography be considered as irrefutable evidence?  The realism may convince all, will convince all, except the expert and the initiated after careful study.  A shrewd judge will insist that in every case the negative be submitted and examined for possible alterations by a clever manipulator.”

Kennedy bent his gaze on McLoughlin.  “Now, I do not accuse you, sir, of anything.  But a photograph has come into the possession of Mr. Travis in which he is represented as standing on the steps of your house with yourself and Mr. Cadwalader Brown.  He and Mr. Brown are in poses that show the utmost friendliness.  I do not hesitate to say that that was originally a photograph of yourself, Mr. Brown, and your own candidate.  It is a pretty raw deal, a fake in which Travis has been substituted by very excellent photographic forgery.”

McLoughlin motioned to Hanford to reply.  “A fake?” repeated the latter contemptuously.  “How about the affidavits?  There’s no negative.  You’ve got to prove that the original print stolen from Travis, we’ll say, is a fake.  You can’t do it.”

“September 19th was the date alleged, I believe?” asked Kennedy quietly, laying down the bundle of metric photographs and the alleged photographs of Travis.  He was pointing to a shadow of a gable on the house as it showed in the metric photographs and the others.

“You see that shadow of the gable?  Perhaps you never heard of it, Hanford, but it is possible to tell the exact time at which a photograph was taken from a study of the shadows.  It is possible in principle and practice and can be trusted.  Almost any scientist may be called on to bear testimony in court nowadays, but you would say the astronomer is one of the least likely.  Well, the shadow in this picture will prove an alibi for some one.