"We ought to get more," said Joe. "The way the cars have gone we'll be
lucky to get more than 2 days out of each one of these."

During the day, Ken's father had directed the preparation of metallic
specimens from samples the boys had brought from Art's garage and from
those the men brought back from the power plant. With the high-powered
electron microscope, photographs were taken.

As they finished their work the boys went with Ken to the laboratory.
Professor Maddox looked up. "Hello, Fellows," he said. "Have you got
your piece of machinery running?"

"Purring like a top," said Ken.

"Expected to run about as long," said Al.

"Have you finished any photomicrographs?" Ken asked. "Do they show
anything?"

His father passed over a wet print. The boys gathered around it.

"It doesn't mean much to me," said Dave Whitaker. "Can you tell us what
it shows?"

Ken's father took a pencil from his pocket and touched it lightly to a
barely perceptible line across the center of the picture. "That is the
boundary," he said, "between the cylinder wall and the piston taken from
one of the samples you brought in."

"I can't see anything that looks like a line between two pieces of
metal," said Ted Watkins. "It looks like one solid chunk to me."

"That is substantially what it is," said Professor Maddox. "There is no
longer any real boundary as there would be between two ordinary pieces
of metal. Molecules from each piece have flowed into the other, mixing
just as two very viscous liquids would do. They have actually become one
piece of metal."

He took up another photograph. "Here you can see that the same thing has
happened in the case of the shaft and bearing samples we obtained from
the Collin's Dam power plant. Molecules of the two separate pieces of
metal have intermingled, becoming one single piece."

"How could they do that?" Ken exclaimed. "Metals can't flow like
liquids."

"They can if the conditions are right. When steel is heated to a
sufficiently high temperature, it flows like water."

"But that's not the case here!"

"No, it isn't, of course. At lower temperatures the molecules of a solid
do not possess the energy of motion which they have in a liquid state.
The metallic surface of a piece of cold steel has a certain surface
tension which prevents the escape of the relatively low-energy
molecules; thus it has the characteristics we ascribe to a solid."

"Then what has happened in this case?" Joe as