! All I want to do
is show you my new 'space eye.'"

[Illustration: Ned Newton, Tom's Chum]

"Can't say as I like that word 'yet,'" Ned muttered darkly. "But I'll
take a look at your new jigger if you'll promise not to shoot me through
space in a rocket or cannon-ball!"

"Word of honor I won't," promised Tom, crossing his heart with mock
solemnity. "Well, here we are."

The two boys had reached the laboratory, a small building at the rear
of the spacious lawn surrounding Tom's father's home and close to the
extensive work of the Swift Manufacturing Company at Shopton.

[Illustration: Tom Crossed His Heart]

"I'll bet these shelves have more scientific apparatus on 'em than any
other shelves in the world," remarked Ned, as his chum opened the door.

Various cabinets containing hundreds of chemicals stood about. Against
one wall was a huge transformer, from which the youthful scientist,
Tom Swift, could draw almost any kind of electric current he might
desire.

[Illustration: They Entered the Laboratory]

"Here goes!" said the young inventor.

He rolled back a small rug in the middle of the floor to expose a
massive steel trap door. This he unlocked by twirling the dial of a
complicated mechanism. Some years before Tom had constructed beneath his
laboratory an impregnable chamber to safeguard his secret plans. He
called it his Chest of Secrets, and guarded it well.

[Illustration: Tom Rolled Back a Small Rug]

Even Ned Newton, Tom's closest friend and business associate, did not
know the entire contents of the massive vault. Only Tom and his father
were aware of all the inventions concealed there.

"Some of these inventions must not be known to the world in its present
state," the elder man had said.

One of them was the terrible electric death-ray, capable of destroying
anything in its path. Only if the United States should be invaded by
an enemy power, would this be revealed.

[Illustration: There Was a Death Ray]

"Here it is," said Tom, joining his chum after a few minutes spent in
the vault.

He was carrying a small wooden box which he placed on the desk and
opened. If Ned, as he leaned over eagerly, expected to see anything
astonishing he was disappointed. Resting on the velvet lining was simply
a round disk of a greenish substance perhaps six inches in diameter.
This was mounted in a gleaming metal ring from the edges of which there
projected five electric binding posts.

[Illustration: He W