We were oblivious to the passage of time, and only a call over our speaking tube diverted our attention.

I opened the door and a few seconds later Long Sin himself entered.

Kennedy looked up inquiringly as the Chinaman approached, holding out a package which he carried.

“A bomb,” he said, in the most matter of fact way.  “I promised to have it placed in your laboratory before night.”

The placid air with which the grotesque looking Chinaman imparted this astounding information was in itself preposterous.  His actions and words as he laid the package down gingerly on the laboratory table indicated that he was telling the truth.

Kennedy and I stared at each other in blank amazement for a moment.  Then the humor of the thing struck us both and we laughed outright.

Clutching Hand had told him to deliver it—­and he had done so!

Hastily I filled a pail with water and brought it to Kennedy.

“If it is really a bomb,” I remarked, “why not put the thing out of commission?”

“No, no, Walter,” he cried quickly, shaking his head.  “If it’s a chemical bomb, the water might be just the thing to make the chemicals run together and set it off.  No, let us see what the new X-ray machine can tell us, first.”

He took the bomb and carefully placed it under the wonderful rays, then with the fluoroscope over his eyes studied the shadow cast by the rays on its sensitive screen.  For several minutes he continued safely studying it from every angle, until he thoroughly understood it.

“It’s a bomb, sure enough,” Craig exclaimed, looking up from it at last to me.  “It’s timed by an ingenious and noiseless little piece of clockwork, in there, too.  And it’s powerful enough to blow us all, the laboratory included, to kingdom come.”

As he spoke, and before I could remonstrate with him, he took the infernal machine and placed it on a table where he set to work on the most delicate and dangerous piece of dissection of which I have ever heard.

Carefully unwrapping the bomb and unscrewing one part while he held another firm, he finally took out of it a bottle of liquid and some powder.  Then he placed a few grains of the powder on a dish and dropped on it a drop or two of the liquid.  There was a bright flash, as the powder ignited instantly.

“Just what I expected,” commented Kennedy with a nod, as he examined the clever workmanship of the bomb.

One thing that interested him was that part of the contents had been wrapped in paper to keep them in place.  This paper he was now carefully examining with a hand lens.

As nearly as I could make it out, the paper contained part of a typewritten chemical formula, which read: 

TINCTURE OF IODINE

Three parts of—–­

He looked up from his study of the microscope to Long Sin.