"'Very good. Now look at this sketch of the hole in the skull, and tell me what you see.'
"Barnes put on his glasses, and gazed attentively for a minute or so, and then looked up. 'The pick point has crashed through without leaving any marks of its edges whatever.'
"'That is to say, there are none of your right-angles showing.'
"'None. But that does not go to prove anything.'
"'No. It's only about a tenth of my proof. It gives the vague initial idea. It made me look more carefully, and I saw this'—I pointed with my pencil to a corner of the sketch.
"Barnes whistled. 'A clean arc of a circle,' said he, 'cut in the bone as though a knife had done it. You saw that pickaxe. Was it much worn? Were the angles much rounded near the point?'
"'They were not. On the contrary, the pick, though an old one, had just been through the blacksmith's shop to be re-sharpened, and had not been used since. There was not a trace of wear upon it: of that I am certain.'
"Barnes whistled again in much perplexity. At length said he, 'It's an absolutely certain thing that Walker was not killed in the way they imagine. But I don't think this will get Guide off scot-free. There's too much other circumstantial evidence against him. Of course you'll do your best, but——'
"'It would be more than a toss up if I could avoid a conviction. Quite so. We must find out more. The question is, how was this wound made? Was there a third man in it?'