"Well, well, so it does, so it does," said Mr. Golden eagerly. "Boys, I certainly congratulate you; you have done a big thing and if it works as well as it seems to be doing, it will be one of the greatest inventions of the day."
"Now," said Jack, "we must see how long it will—hold on a minute," and to their amazement he rushed to the back door flung it open and dashed across the yard. He was gone fully five minutes and when he returned was panting for all he was worth.
"Didn't you see him?" he demanded.
"See who?" asked Bob.
"Why, sure as I live, Fred Jenkins was looking in that window. He lit out, though, and got away before I could get out."
"What do you suppose he wanted?" asked Mr. Golden.
"Well, I'll tell you, dad," replied Bob. "Ever since we came down from the lake Fred and Will Jenkins have been trying to find out what we've been doing. You know they almost got us on that new vibrator we invented, owing to our carelessness in leaving it on the table one day when they came in."
"Yes," broke in Jack, "and they are just mean enough to sneak round and try to steal our new storage cell."
"We've got to be mighty careful this time," continued Bob, "and not let one of those caps get into their hands, for the secret of the whole thing is in them, as it is the action of the different metals composing them which starts the manganese dioxide to decomposing and converts its chemical energy into electricity."
"Well, come on boys," said Mr. Golden as soon as Bob had finished. "Your mother sent me down to tell you to come to supper, and we mustn't be late, as she has company."