Larry felt greatly disappointed. He had expected something that would point a clew to the burglars, and to learn that the paper had only been marked by an acid, was somewhat of a shock. “Could nitric acid, such as is used in the explosive nitro-glycerine, produce that color?” was Mr. Newton’s next question. “Of course it could,” said Mr. Hosfer. “I knew you were coming to some terrible explosion, some awful blowing up of innocent persons, some catastrophe, some horrible cataclysm, some terrific disturbance of the laws of nature!” “Not quite as bad as that,” said Mr. Newton. “But tell me this: If nitric acid made those marks, and nitro-glycerine could do it, would a person handling the explosive be likely to mark a paper in that fashion?” “Most decidedly so,” said Mr. Hosfer. “I can refer you to——” “Never mind!” interrupted Mr. Newton. “That is all I want to know.” “What are you going to do now?” asked the chemist. “I am going to look for the man who made those marks on the paper,” replied the reporter. “How can you find him?” asked Larry, in surprise. “By looking for a man with a blue hand,” was Mr. Newton’s answer. CHAPTER XI A SEARCH FOR THE BLUE HAND “What do you mean?” asked Mr. Hosfer, as he watched Mr. Newton place what was left of the blue paper in his pocket. “I mean that I have a clew to the persons who blew open the safe,” said Mr. Newton. “As soon as I saw that paper which Larry found, with the blue marks on it, I thought it might have been used by the burglars. I was at a loss to know what could have caused the marks, but you, Mr. Hosfer, have solved that problem for me. I think I can manage the rest.” “But can’t the blue marks wash off?” asked Larry. “What good is the clew then?” “No! The blue marks will not come off!” exclaimed Mr. Newton. “Will they, Mr. Hosfer?” “Not for some time,” replied the chemist. “I see now what Mr. Newton is driving at. He is going to solve a horrible, a dastardly, soul-curdling, bloody mystery. The blue marks will not come off. It is a peculiar feature of certain forms of nitric acid, and also of nitro-glycerine, which is made from the acid, that they will stain the skin a bluish color. This color will not come off until the skin wears off, and, as that takes some time, you may be sure that your blue-handed man will have to go around for a number of weeks with the marks on his fingers and thumb. I see what Mr. Newton is up to now. Oh, but you’re a sly dog!” “It’s mostly a matter of luck,” replied the reporter. “You have been of great service to us, Mr. Hosfer.” “To think I should be mixed up in a terrible, fearful, awful, shocking, sensational affair like this,” spoke the chemist, with a smile, as though it was the best fun in the world. “That comes of having a reporter for a friend.” “Well,” said Mr. Newton, “you ought to be glad of a chance to aid the ends of justice by discovering the safe-robber.”