I yielded the spectroscope to him, and scarcely had he looked into it ere he cried out—
"By all that's wonderful, the spectrum has changed. Eureka! It's thallium now. I should know that splendid green line amongst a thousand."
"Thallium!" I exclaimed, astonished in my turn.
"Yes," responded Gazen, hurriedly. "Make a note of the observation, and also of the time. You will find a book for the purpose lying on the desk."
I did as directed, and awaited further orders. The silence was so great that I could plainly hear the ticking of my watch laid on the desk before me. At the end of several minutes the professor cried—
"It has changed again: make another note."
"What is it now?"
"Sodium. The yellow bands are unmistakable."
A deep stillness reigned as before.
"There she goes again," exclaimed the professor, much excited. "Now I can see a couple of blue lines. What can that be? I believe it's indium."