A knock sounded at the door of Dr. Bird's private laboratory in the Bureau of Standards. The famous scientist paid no attention to the interruption but bent his head lower over the spectroscope with which he was working. The knock was repeated with a quality of quiet insistence upon recognition. The Doctor smothered an exclamation of impatience and strode over to the door and threw it open to the knocker. "Oh, hello, Carnes," he exclaimed as he recognized his visitor. "Come in and sit down and keep your mouth shut for a few minutes. I am busy just now but I'll be at liberty in a little while." [Illustration] "There's no hurry, Doctor," replied Operative Carnes of the United States Secret Service as he entered the room and sat on the edge of the Doctor's desk. "I haven't got a case up my sleeve this time; I just came in for a little chat." "All right, glad to see you. Read that latest volume of the _Zeitschrift_ for a while. That article of Von Beyer's has got me guessing, all right." Carnes picked up the indicated volume and settled himself to read. The Doctor bent over his apparatus. Time and again he made minute adjustments and gave vent to muttered exclamations of annoyance at the results he obtained. Half an hour later he rose from his chair with a sigh and turned to his visitor. "What do you think of Von Beyer's alleged discovery?" he asked the operative. * * * * * "It's too deep for me, Doctor," replied the operative. "All that I can make out of it is that he claims to have discovered a new element named 'lunium,' but hasn't been able to isolate it yet. Is there anything remarkable about that? It seems to me that I have read of other new elements being discovered from time to time." "There is nothing remarkable about the discovery of a new element by the spectroscopic method," replied Dr. Bird. "We know from Mendeleff's table that there are a number of elements which we have not discovered as yet, and several of the ones we know were first detected by the spectroscope. The thing which puzzles me is that so brilliant a man as Von Beyer claims to have discovered it in the spectra of the moon. His name, lunium, is taken from Luna, the moon." "Why not the moon? Haven't several elements been first discovered in the spectra of stars?"