“Some powdered metallic aluminum mixed with oxide of iron,” whispered Constance in return.  “I read of this thing in a scientific paper the other day, and I determined to get some of it.  But I didn’t think I’d ever really have occasion to use it.”

She added some powder from the other vial.

“And that?”

“Magnesium powder.”

Constance had lighted a match.

“Stand back, Anita,” she whispered, “back, Anita,” she whispered, “back in the farthest corner of the room, and keep quiet.  Shut your eyes—­turn your face away!”

There was a flash, blinding, then a steady, brilliant burst of noiseless, penetrating, burning flame.

Anita had expected an explosion.  Instead she found that her eyes hurt.  She had not closed them tightly quick enough.

Still, Constance’s warning had been sufficient to prevent any damage to the sight, and she slowly recovered.

Actually, the burning powder seemed to be sinking into the very steel of the safe itself, as if it had been mere ice!

Was it an optical illusion, a freak of her sight?

“Wh-what is it!” she whispered in awe, drawing closer to her friend.

“Thermit,” whispered Constance in reply, as the two watched the glowing mass fascinated, “an invention of a German chemist named Goldschmidt.  It will burn a hole right through steel—­at a terrific temperature, three thousand or more degrees.”

The almost burned out mass seemed to fall into the safe as if it had been a wooden box instead of chrome steel.

They waited a moment, still blinking, to regain control over their eyes in spite of the care they had used to shield them.

Then they tiptoed across the floor.

In the top of the safe yawned a hole large enough to stick one’s hand and arm through!

Constance reached into the safe and drew out something on which she flashed the pocket light.

There was bundle after bundle of checks, the personal checks of a methodical business man, carefully preserved.

Hastily she looked them over.  All seemed to be perfectly straight—­ payments to tradesmen, to real estate agents, payments of all sorts, all carefully labeled.

“Oh, he’d never let anything like that lie around,” remarked Anita, as she began to comprehend what Constance was after.

Constance was scrutinizing some of the checks more carefully than others.  Suddenly she held one up to the light.  Apparently it was in payment of legal services.

Quickly she took the little bottle of brownish fluid which she had brought with the sponge.

She dipped the sponge in it lightly and brushed it over the check.  Then she leaned forward breathlessly.

“Eradicating ink is simply a bleaching process,” she remarked, “which leaves the iron of the ink as a white oxide instead of a black oxide.  The proper reagent will restore the original color—­ partially and at least for a time.  Ah—­yes—­it is as I thought.  There have been erasures in these checks.  Other names have been written in on some of them in place of those that were originally there.  The sulphide of ammonia ought to bring out anything that is hidden here.”