"I know we've got to have a condenser, but I'm blessed if I really understand what it is for," said Joe. "I know the doctor told us about it, but I guess I didn't get a very clear idea of what it was all about."
"I'm not very clear on it either," admitted Bob. "But from what he said and what I've read, it seems to be a sort of equalizer, for the electric current, storing it up when it's strong and giving it out when it's weak. It prevents the current getting too strong at times and burning something out."
"That's the way I understood it, too," said Herb. "And Dr. Dale said that in the larger sets they have what they call a variable condenser, so that they can get more or less damping action according to the strength of the incoming current waves."
"I guess I get the idea," said Joe. "But it's a pretty complicated thing when you first tackle it, isn't it?"
"Yes, but it's just like almost anything else, probably—it's easy when you know how," said Bob.
"It tells here how to make the condenser," said Herb, who had been looking over an instruction book that the boys had bought. "But it says the best thing to use for the plates is tinfoil. Now, where are we going to get the tinfoil from, I'd like to know!"
"If you want to know real badly, I'll tell you," said Bob. "Right out of that box over in the corner. Just wait a minute and I'll show you."
Bob stepped swiftly over to the box in question and produced a big ball of tinfoil, composed of separate sheets tightly packed together.
"When I was a kid I used to collect this stuff and sell it to the junkman," he said. "This ball never got big enough for that, and I forgot all about it until a few days ago when I happened to come across it and thought that it would be just the thing for us to use now. We can easily peel off all the sheets we need, I guess. Some of them are damaged, but there are enough whole ones to do our trick."
"Gee, that's fine!" said Joe. "Pry off some, Bob, and let's see if it will serve."