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."

Another long pause ensued.

"Now they are gone," ejaculated Gazen once more. "A red and a yellow line have taken their place. That should be lithium. Hey, presto!—and all was dark."

"What's the matter?"

"It's all over." With these words he removed the spectroscope from the telescope, and gazed anxiously at the planet "The light is gone," he continued, after a minute. "Perhaps another cloud is passing over it. Well, we must wait. In the meantime let us consider the situation. It seems to me that we have every reason to be satisfied with our night's work. What do you think?"

There was a glow of triumph on his countenance as he came and stood before me.

"I believe it's a signal," said I, with an air of conviction.

"But how?"

"Why should it change so regularly? I've timed each spectrum, and found it to last about five minutes before another took its place."

The professor remained thoughtful and silent.

"Is it not by the light which comes from them that we have gained all our knowledge of the constitution of the heavenly bodies?" I continued. "A ray from the remotest star brings in its heart a secret message to him who can read it. Now, the Martians would naturally resort to the same medium of communication as the most obvious, simple, and practicable. By producing a powerful light they might hope to attract our attention, and by imbuing it with characteristic spectra, easily recognised and changed at intervals, they would distinguish the light from every other, and show us that it must have had an 

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