places where they had good times. In the family was also Uncle
Pennywait. That wasn't his real name, but the children called him that
because he so often said:

"Wait a minute and I'll give you a penny."

Hal and Mab used to buy lollypops with the pennies their uncle gave
them. And then--Oh, yes, I mustn't forget Roly-Poly, the funny, fat,
poodle dog who was always hiding things in holes in the ground,
thinking they were bones, I guess. Sometimes he would even hide Aunt
Lolly's spectacles and she would have the hardest work finding them.
Oh, such hard work!

"Well, Daddy," asked Mab, after Mr. Blake had sat silent for some
time, "have you thought of a way to tell us what makes the shiny stuff
in the--in the--in the--Oh! I can't say that big word!" she finished
with a sigh.

"The mercury in the thermometer!" laughed Daddy Blake. "You want to
know what makes it go down? Well, it's the cold. You see cold makes
anything get smaller and shrink, and heat makes things swell up, and
get larger. That's why the steam from hot water swells up and makes
the engine go, and pull the cars.

"And in hot weather the mercury swells, puffs itself out and creeps
up inside the little glass tube. In winter the mercury gets cold, and
shrinks down, just as it is doing to-night."

"But will it get cold enough so you can tell us the secret?" Hal
wanted to know, most anxiously.