“I examined the walls of Dr. Kharkoff’s house, and fortunately was able to pick out a few small fragments of the contents of the bomb which had been thrown out before the flame ignited them.  I have analysed them, and find them to be a peculiar species of blasting-gelatine.  It is made at only one factory in this country, and I have a list of purchasers for some time back.  One name, or rather the description of an assumed name, in the list agrees with other evidence I have been able to collect.  Moreover, the explosive was placed in a lead tube.  Lead tubes are common enough.  However, there is no need of further evidence.”

He paused, and the revolutionists stared fixedly at the fragments of the now harmless bomb before them.

“The exploded bomb,” concluded Craig, “was composed of the same materials as this, which I found unexploded at the door of Miss Nevsky’s room—­the same sort of lead tube, the same blasting-gelatine.  The fuse, a long cord saturated in sulphur, was merely a blind.  The real method of explosion was by means of a chemical contained in a glass tube which was inserted after the bomb was put in place.  The least jar, such as opening a door, which would tip the bomb ever so little out of the horizontal, was all that was necessary to explode it.  The exploded bomb and the unexploded were in all respects identical—­the same hand set both.”

A gasp of astonishment ran through the circle.  Could it be that one of their own number was playing false?  In at least this instance in the warfare of the chemist and the dynamiter the chemist had come out ahead.

“But,” Kennedy hurried along, “the thing that interests me most about this case is not the evidence of the bombs.  Bombs are common enough weapons, after all.  It is the evidence of almost diabolical cunning that has been shown in the effort to get rid of the father of the revolution, as you like to call him.”

Craig cleared his throat and played with our feelings as a cat does with a mouse.  “Strange to say, the most deadly, the most insidious, the most elusive agency for committing murder is one that can be obtained and distributed with practically no legal restrictions.  Any doctor can purchase disease germs in quantities sufficient to cause thousands and thousands of deaths without giving any adequate explanation for what purpose he requires them.  More than that, any person claiming to be a scientist or having some acquaintance with science and scientists can usually obtain germs without difficulty.  Every pathological laboratory contains stores of disease germs, neatly sealed up in test-tubes, sufficient to depopulate whole cities and even nations.  With almost no effort, I myself have actually cultivated enough germs to kill every person within a radius of a mile of the Washington Arch down the street.  They are here in these test-tubes.”

We scarcely breathed.  Suppose Kennedy should let loose this deadly foe, these germs of death, whatever they were?  Yet that was precisely what some fiend incarnate had done, and that fiend was sitting in the room with us.