It gave back a silvery sound, but it did not break.

Another and more violent blow. The same result.

"It is unbreakable glass!" said Evans.

It appeared as though the pane was made of glass toughened on the
Siemens system--as after several blows it remained intact.

The light had now increased, and Phil Evans could see for some
distance within the radius allowed by the frame.

"What do you see?" asked Uncle Prudent.

"Nothing."

"What? Not any trees?"

"No."

"Not even the top branches?"

"No."

"Then we are not in the clearing?:

"Neither in the clearing nor in the park."

"Don't you see any roofs of houses or monuments?" said Prudent, whose
disappointment and anger were increasing rapidly.