Then Selwyn placed several cubes in a mortar, pounded them to powder with an iron pestle, and, measuring out the tiniest pinch—­scarcely enough to cover the point of a penknife, placed a few grains in several paper cartridges.  Two wads followed the powder, then an ounce and a half of shot, then a wad, and then the crimping.

The guests stepped gratefully outside; Selwyn, using a light fowling-piece, made pattern after pattern for them; and then they all trooped solemnly indoors again; and Selwyn froze Chaosite and boiled it and baked it and melted it and took all sorts of hair-raising liberties with it; and after that he ground it to powder, placed a few generous pinches in a small hand-grenade, and affixed a primer, the secret composition of which he alone knew.  That was the key to the secret—­the composition of the primer charge.

“I used to play base-ball in college,” he observed smiling—­“and I used to be a pretty good shot with a snowball.”

They followed him to the cliff’s edge, always with great respect for the awful stuff he handled with such apparent carelessness.  There was a black sea-soaked rock jutting out above the waves; Selwyn pointed at it, poised himself, and, with the long, overhand, straight throw of a trained ball player, sent the grenade like a bullet at the rock.

There came a blinding flash, a stunning, clean-cut report—­but what the others took to be a vast column of black smoke was really a pillar of dust—­all that was left of the rock.  And this slowly floated, settling like mist over the waves, leaving nothing where the rock had been.

“I think,” said Edgerton Lawn, wiping the starting perspiration from his forehead, “that you have made good, Captain Selwyn.  Dense or bulk, your Chaosite and impact primer seem to do the business; and I think I may say that the Lawn Nitro-Powder Company is ready to do business, too.  Can you come to town to-morrow?  It’s merely a matter of figures and signatures now, if you say so.  It is entirely up to you.”

But Selwyn only laughed.  He looked at Austin.

“I suppose,” said Edgerton Lawn good-naturedly, “that you intend to make us sit up and beg; or do you mean to absorb us?”

But Selwyn said:  “I want more time on this thing.  I want to know what it does to the interior of loaded shells and in fixed ammunition when it is stored for a year.  I want to know whether it is necessary to use a solvent after firing it in big guns.  As a bursting charge I’m practically satisfied with it; but time is required to know how it acts on steel in storage or on the bores of guns when exploded as a propelling charge.  Meanwhile,” turning to Lawn, “I’m tremendously obliged to you for coming—­and for your offer.  You see how it is, don’t you?  I couldn’t risk taking money for a thing which might, at the end, prove dear at any price.”

“I cheerfully accept that risk,” insisted young Lawn; “I am quite ready to do all the worrying, Captain Selwyn.”