“Exactly; but how would you do that?”
“Oh, it’s easy enough, I believe,” said Tom. “You get a sheet of tinfoil, lay it on a table, cover it with quicksilver, and then put the glass on it, and press it with weights till the tinfoil and quicksilver stick to the glass, and then you have a regular mirror.”
“You seem to know all about it, Tom,” said the Vicar, who had dropped in for a chat, and to hear how the telescope was going on.
“I read it somewhere,” said Tom.
“And he can always recollect this sort of thing,” said his uncle; “but never could remember anything to do with the law.”
Tom looked at him reproachfully.
“Well,” continued Uncle Richard, “your process would do for ordinary looking-glasses, Tom, but not for an optical reflector.”
“Why, uncle?”
“Because the rays of light would have to pass through the thickness of the glass before they reached the reflecting surface,—the quicksilver,—and in so doing they would be refracted—broken-up and discoloured—so that the reflection would most likely be doubled when it came away; that is, you would see one reflection from the silver at the back, and another from the surface of the glass.”
“Therefore,” said the Vicar, “we must decline friend Tom’s ingenious proposal, and take yours, Brandon, for as usual you have a plan ready.”