Leaning down to the scuttle, he called, “Jenkins—­my field-glasses—­quick!”

One of his men handed them to him and he adjusted them, gazing off intently.  There he could see what looked like a squad of cavalry galloping along headed by an officer and a rough looking individual.

“Come—­we must get ready for an attack!” he shouted diving down the scuttle again.

In the laboratory dining-room, his men, recalled, hastily took his orders.  Each of them seized one of the huge black rubber newly completed gas bombs and ran out, making for a grove near-by.

Quickly as Del Mar had acted, it was not done so fast but that the troop of cavalry as they pulled up on the top of a hill and followed the directing finger of the tramp could see men running to the cover of the grove.

“Forward!” shouted Woodward.

As if all were one machine, the men and horses shot ahead, until they came to the grove about the old hotel.  There they dismounted and spread out in a semi-circular order, advancing on the grove.  As they did so, shots rang out from behind the trees.  Del Mar’s men, from the shelter were firing at them.  But it seemed hopeless for the fugitives.

“Ready!” ordered Del Mar as the cavalrymen advanced, relentless.

Each of his men picked up one of the big black gas bombs and held it high up over his head.

“Come on!” urged Woodward.

His men broke into a charge on the grove.

“Throw them!” ordered Del Mar.

As far as he could hurl it, each of the men sent one of the black globes hurtling through the air.  They fell almost simultaneously, a long line of them, each breaking into a thousand bits.  Instantly dense, greenish-yellow fumes seemed to pour forth, enveloping everything.  The wind which Del Mar had carefully noted when he chose the position in the grove, was blowing from his men toward the only position from which an attack could be made successfully.

Against Woodward’s men as they charged, it seemed as if a tremendous, slow-moving wall of vapor were advancing from the trees.  It was only a moment before it completely wrapped them in its stifling, choking, suffocating embrace.  Some fell, overcome.  Others tried to run, clutching frantically at their throats and rubbing their eyes.

“Get back—­quick—­till it rolls over,” choked Woodward.

Those who were able to do so, picked up their stupefied comrades and retreated, as best they could, stumbling blindly back from the fearful death cloud of chlorine.

Meantime, under cover of this weird defence, Del Mar and his men, their own faces covered and unrecognizable in their breathing masks and goggles, dashed to one side, with a shout and disappeared walking and running behind and even through the safety of their impregnable gas barrier.

More slowly we of the hunt had followed Woodward’s cavalry until, some distance off, we stood, witnessing and wondering at the attack.  To our utter amazement we saw them carrying off their wounded and stupefied men.  We hurried forward and gathered about, offering whatever assistance we could to resuscitate them.