failure of it," and the man spoke somewhat bitterly.
"Never mind, Mr. Sharp," went on Tom Swift, "I think it will be the last mistake. I see what the trouble is now; and know how to remedy it. Come on back, and we'll try it again; that is if the tank hasn't blown up."
"No, I guess that's all right. It was the aluminum container that went up, and that's so light it didn't do much damage. But we'd better wait until some of those fumes escape. They're not healthy to breathe."
The cloud of yellowish smoke was slowly rolling away, and the man and lad were approaching the shop, which, in spite of the explosion that had taken place in it, was still intact, when an aged man, coming from a handsome house not far off, called out:
"Tom, is anyone hurt?"
"No, dad. We're all right."
"What happened?"
"Well, we had another explosion. We can't seem to get the right mixture of the gas, but I think we've had the last of our bad luck. We're going to try it again. Up to now the gas has been too strong, the tank too weak, or else our valve control is bad."
"Oh dear, Mr. Swift! Do tell them to be care-
