Then followed a dull, rumbling roar, not as loud as might have been expected, but awful in its intensity.Deep down under the very foundations of the earth it seemed to rumble.
"Run! Run back!" cried Tom Swift."There's a back-draft and the powder gas is poisonous.Stoop down and run back!"They understood what he meant.The vapor from the powder was deadly if breathed in a confined space.Even in the open it gave one a terrible headache.And Tom could see floating out of the tunnel the first wisps of smoke from the fired explosive.It was lighter than air, and would rise.Hence the necessity, as in a smoke-filled room, of keeping low down where the air is purer.
They all rushed back, stooping low.Mr.Damon stumbled and fell, butKoku picked him up and, tucking him under one arm, as he might have done a child, the giant followed Tom to a place of safety.
"Well, Tom, it went off all right," said Mr.Job Titus, as they stood among the shacks of the workmen and watched the smoke pouring out of the tunnel mouth.
"Yes, it went off.But did it do the work? That's what we've got to find out."They waited impatiently for the deadly vapor to clear out of the tunnel.It was more than an hour before they dared venture in, and then it was with smarting eyes and puckered throats.But the atmosphere was quickly clearing.
"Switch on the lights," cried Tom to Tim, for the illuminating current had been cut off when the blast was fired."Let's see what we've brought down."Following the eager young inventor came the contractors, some of the white workers, Mr.Damon and Professor Bumper.The little scientist said he would like to see the effect of the big blast.
Along they stumbled over pieces of rock, large and small.
"Some force to it," observed Job Titus, as he observed pieces of rock close to the mouth of the tunnel."If it only exerted the force the other way, against the face of the rock, as well as back this way, we'll be all right.""The greater force was in the opposite direction," Tom said.
A big search-light had been got ready to flash on the place where the blast had been set off.This was to enable them to see how much rock had been torn away.And, as they reached the place where the flint-like wall had been, they saw a strange sight.
"Bless my strawberry short-cake!" gasped Mr.Damon."What a hole!" "It is a bole," admitted Tom, in a low voice."A bigger hole than Idared hope for."
For a great cave, seemingly, had been blown in the face of the rock wall that had hindered the progress of the tunnel.A great black void confronted them.
"Shift the light over this way," called Tom to Walter Titus, who was operating it."I can't see anything."The great beam of light flashed into the void, and then a murmur of awe came from every throat.
For there, revealed in the powerful electrical rays, was what seemed to be a long tunnel, high and wide, as smooth as a paved street.And on either side of it were what appeared to be buildings, some low, others taller.And, branching off from the main tunnel, or street, were other passages, also lined with buildings, some of which had crumbled to ruins.
"Bless my dictionary!" cried Mr.Damon."What is it?"Professor Bumper had crawled forward over the mass of broken rock.He gazed as if fascinated at what the searchlight showed, and then he cried:
"I have found it! I have found it! The hidden city of Pelone!"
