The children giggled, especially at the last bit. “You are an idiot, Fatty,” said Pip. “It’s a good thing old Clear-Orf won’t get the letter.”
“Oh, we’ll send it all right,” said Fatty, “but as it’s written in invisible ink he won’t be able to read it, poor mutt!”
There was nothing to be seen on the sheet of notepaper. The orange-juice ink was certainly invisible!
“But, Fatty, how can any one read invisible writing?” said Daisy.
“Easy,” said Fatty. “I’ll show you how to read this kind. Got an electric iron anywhere?”
“Yes,” said Pip. “But I don’t expect Mother would let us have it. She seems to think that anything she lends us is bound to get broken. Anyway, whatever do yo want an iron for?”
“Wait and see,” said Fatty. “Haven’t you got an ordinary flat-iron, Pip, if we can’t borrow the electric one? There must be one in the kitchen.”
There was. The cook said Pip might have it. “If you break that, I’d be surprised!” she said, and Pip sped upstairs carrying the heavy old iron.
“Heat it on the fire,” said Fatty. So it was put on the fire, and well heated. When Fatty judged that it was warm enough, he took it off the fire, being careful to hold it with an iron-holder.
“Now watch,” he said, and in excitement they all watched. Fatty ran the iron lightly over the sheet on which he had written his invisible letter.