llow you to hold
your hand in it without its hurting you. But then you would have to mind
where you held your hand; because where the steam began to condense
again, it would be boiling hot."

"I had rather take your word for the experiment than try it, young
gentleman," Mr. Bagges observed.

"Another very curious thing," proceeded Harry, "in regard to boiling,
has been discovered lately. A kettle might be too hot to boil water in.
Take a little bar of silver, heated very highly; dip it into water. At
first, you have no boiling, and you don't have any at all till the
silver has cooled some degrees. Put a drop of water into a platinum
dish, heated in the same way, and it will run about without boiling till
the heat diminishes; and then it bursts into steam. M. Boutigny, the
French chemist, made this discovery. Vapor forms between the drop of
water and the red-hot metal, and, being a bad conductor of heat, keeps
the heat of the metal for some time from flowing into the water. Owing
to this, water, and mercury even, may be frozen in a red-hot vessel if
the experiment is managed cleverly. A little more than a couple of
centuries ago, this would have been thought witchcraft."

"And the philosopher," added Mr. Bagges, "would have been fried instead
of his water-drop. Let me see--eh? what do they call this singular state
of water?"

"The spheroidal state," answered Harry. "However, that is a state that
water does not get into in a kettle, because kettles are not allowed to
become red hot, except when they are put carelessly on the fire with no
water in them, or suffered to remain there after the water has boiled
quite away!"

"Which is ruination to kettles," Mrs. Wilkinson observed.

"Of course it is, mamma, because at a red heat iron begins to unite with
oxygen, or to rust. Another thing that injures kettles is the fur that
collects in them. All water in common use contains more or less of
earthy and other salts. In boiling, these things separate from the
water, and gradually form a fur or crust inside the kettle or boiler."

"And a nice job it is to get rid of it," said his mamma.

"Well, chemistry has lessened that difficulty," replied Harry. "The fur
is mostly carbonate of lime. In that case, all you have to do is to boil
some sal-ammoniac--otherwise muriate, or more properly hydrochlorate of
ammonia--in the furred vessel. The hydrochloric acid unites with the
lime, and the carbonic acid goes to the ammonia. Both t