"More powder!" cried Tom. "Why, this is the most I have ever set off."
"Then somethin's wrong, sor. Fer there's only a little rock down. Come an' see fer yersilf."
Tom hastened in. As the foreman had said, the effect of the blast was small indeed. Only a little rock had been shaled off. Tom picked up some of this and took it outside for examination.
"Why, it's harder than the hardest flint we've found yet," he said. "The powder didn't make any impression on it at all. I'll have to use terrific charges."
This was done, but with little better effect. The explosive, powerful as it was, ate only a little way into the rock. Blast after blast had the same poor effect.
"This won't do," said Job Titus, despairingly, one day. "We aren't making any progress at all. There's a half mile of this rock, according to my calculations, and at this rate we'll be six months getting through it. By that time our limit will be up, and we'll be forced to give up the contract What can we do, Tom Swift?"
Chapter XXI
A New Explosive
The young inventor was idly handling some pieces of the very hard rock that had cropped out in the tunnel cut. Tom had tested it, he had pulverized it (as well as he was able), he had examined it under the microscope, and he had taken great slabs of it and set off under it, or on top of it, charges of explosive of various power to note the effect. But the results had not been at all what he had hoped for.