“We have then a negro, but one not engaged in the usual employment of the negro residents in Boston, to look for; next you found clutched in the fingers of the dead girl two threads of brownish color and coarse material, together with a fragment of paper like a part of an envelope on which was written a few notes of music.” “Yes, and I defy the devil to make anything result from such infinitesimal particles of evidence,” exclaimed the professional detective. “Well, I’m not the devil.” said Chapman, quietly proceeding to recapitulate the process adopted by him. “From the few notes—you know that I am something of a musician—I began, _poco a poco_, as they say in music, to reconstruct the tune of which the few notes were a part. As I proceeded, going over the notes time and again on my violoncello, I became convinced that I had heard that wild tune before, and am now able to say where and when.” “Wonderful, perfectly wonderful if you can, Chapman,” cried the thoroughly interested Chief. “What next?” O’Brien asked, impatient at the calmness of the man on the opposite side of the desk. “To-day I saw the finger that the fragment of nail found in the girl’s neck would fit, and one finger-nail had been broken and was gone,” continued Chapman, by great effort restraining the evidence of the exultation that he felt. “Where, man, where? And whose was the hand?” gasped O’Brien. “Wait a moment! Upon reflection I realized that the only part of a man’s apparel likely to give way in a desperate struggle would be a coat pocket; that the hand of the girl had grasped the edge of the pocket and in so doing had closed upon an old envelope in the pocket, which was torn and remained in her hand with a couple of threads from the cloth of the coat when the murderer finally wrenched the coat out of her lifeless fingers.” “Quite likely,” exclaimed the Chief impatiently. “But hurry along, man,” urged the officer. “This afternoon I examined under the most powerful microscope procurable in Boston the threads that your assistant has in safe keeping. I recognized the color and material of which those threads are made. I know the coat whence the threads came, and the owner of the coat,” declared Chapman emphatically. “His name,” almost yelled the astonished detective. “David Chapman,” was the cool and triumphant reply. The Chief glared at the exultant amateur with wonder, in which a doubt of the man’s sanity was mingled.