view_ regularly, and Mike occasionally
sent a package of the printing trade magazines that he found lying
around the shop. Fred picked up many hints from these and thus secured
quite a good start in his knowledge of the printing trade.

The "official photographer" had been equally successful. One day, while
up on the levee trying to take a satisfactory picture of an elusive
"mackerel sky," which was changing from moment to moment, he met a
stranger. This stranger was sitting on a log that projected into the
river, holding a rod and line, and landing fish with an accustomed
skill.

"What in blazes are you trying to photograph?" he said after a while, as
he watched the lad focussing his camera earthwards on what looked like a
piece of black glass, which projected from the stand.

"Clouds, sir," answered Ralph.

"When I try to photograph clouds I look at the sky, not on the ground,"
the stranger remarked. "What's that contrivance you've got on your
camera stand, anyway?"

"It's just a broken piece of looking glass," said the boy, "but I
painted it on the back with black enamel."

"What for?"

"So that I could get at the clouds easier, sir," the boy replied. "I
read how to do that in a book I've got."

"I don't see why black glass should make any difference," said the
fisherman, getting up from the log and coming over to where the boy was
standing.

"It does, sir. If you look on the glass," said Ralph, "you'll see. The
clouds are ever so much sharper."

The stranger looked in. Even the fleecy white clouds, scarcely visible
in the blue sky overhead, stood out a clear white against the blackness
of the mirror. The blue sky was not reflected in the glass.

"That's queer," said the stranger, "the blue hardly shows at all. I
wonder why?"

"It said in the book," Ralph explained, "that the blue didn't show up so
much because it was partly polarized. I couldn't quite understand what
that meant. As far as I could make out, the blue color of the sky is due
to waves that are scattered sideways instead of coming straight down
like the white light does."

"I suppose it is polarized," said the fisherman, "but it hadn't ever
occurred to me that the sky wouldn't be reflected in a black mirror.
You're right, though. The clouds do stand out well! You ought to be able
to get some good pictures from your mirror."

"I have got a lot, sir," said Ralph. "I've made three cloud photographs
every day, rain or shine, for over two m