ower that shall transcend
infinitely anything the imagination of any storyteller ever invented.
Now, what do you say? for I must not preach any more."

"Say, uncle!" cried Tom. "Let's begin at once!"

"I beg pardon, sir," said a pleasant voice; "but would you mind having a
bell made to ring right in here?"

"No, Mrs Fidler," said Uncle Richard; "we will lay down iron pipes
underground to make a speaking-tube, so that you can call when you want
me. What is it--lunch?"

"Lunch, sir!" said Mrs Fidler; "dear me, no; the dinner's waiting and
getting cold."

"Bother the old dinner!" thought Tom.

"Come, my lad, we must eat," said Uncle Richard, with a smile. "We
shall not finish the telescope to-day."

CHAPTER TWELVE.

"Now then, we'll begin," said Uncle Richard; "and the first thing is to
make our mould or gauge, for everything we do must be so exact that we
can set distortion at defiance. We must have no aberration, as
opticians call it."

"Begin to polish the glass, uncle?"

"Not yet. Fetch those two pieces of lath." Tom fetched a couple of
thin pieces of wood, each a little over twelve feet long. These were
laid upon the bench and screwed together, so as to make one rod just
over twenty-four feet long.

Then at one end a hole was made, into which a large brass-headed nail
was thrust, while through the other end a sharp-pointed bradawl was
bored, so as to leave its sharp point sticking out a quarter of an inch
on the other side.

"So far so good," said Uncle Richard. "Do you know what we are going to
do, Tom?" Tom shook his head.

"Strike the curve on that piece of zinc that we are to make our
speculum."

"Curve?" said Tom; "why, it's quite round now."

"Yes; the edge is, but we are going to work at the face."

"But arn't you going to polish it into a looking-glass?"

"Yes; but not a flat one--a plane. That would be of no use to us, Tom;
we must have a parabolic curve."

"Oh," said Tom, who only knew parabolas from a cursory acquaintance with
them through an old Greek friend called Euclid.

"Be patient, and you'll soon understand," continued Uncle Richard, who
proceeded to secure the sheet of zinc to a piece of board by means of
four tacks at its corners, and ended by carrying it out, and fixing the
board just at the bottom of the border, close to the window.

A couple of strong nails at the sides of the board were sufficient, and
then he led the way in.

"Now, Tom, take that ball