t it, and Jonas told him that he had been reading about it in a
book on astronomy.

"Your father let me have the book," said he; "and see my chalk marks for
the sun's shadow."

Rollo looked, and found that Jonas had put down quite a number of chalk
marks along in a line, where they had first began to mark the place
where the shadow of the door reached into. Rollo and Lucy had forgotten
all about their plan of making such a series of observations; but Jonas
had gone on regularly, making a mark every Monday, at noon, precisely.
As the sun, at that season of the year, was going round farther and
farther to the south every week, it shone in farther and farther upon
the floor, so that each chalk mark was farther in than the one made the
week before.

In order to make his marks at the right time, Jonas wanted to know,
every Monday, when it was precisely twelve o'clock, and this led him to
make his noon mark, having seen the account of it in the book which
Rollo's father had lent him. He learned there that the shadows of all
upright objects are cast exactly north at twelve o'clock, or rather very
nearly north; near enough for his purposes. Now, as the post of the barn
door was upright, he knew that the shadow of it would be in the north
and south line at noon. Of course, if he had a north and south line, or
a meridian line, as it was called in the book, drawn upon the floor, he
knew that he could tell when it was noon, by the shadow of the post
coming then exactly upon that line. He explained this all to Rollo, and
Rollo was very much pleased with it indeed. He determined to have a noon
line somewhere in the house.

Rollo asked Jonas what was the way to draw a noon line. Jonas told him
that there were several ways. One way, he said, was to observe some day,
by the clock, when it was exactly noon, and then to mark, upon the barn
floor, the line where the shadow of the edge of the post fell precisely
at that moment. Another way was to get a compass needle, and put it down
upon the floor, and then draw a north and south line precisely in the
direction that the needle indicated. That would, of course, be a north
and south line, because the compass needle always pointed north and
south. He said that he adopted both these methods to make his noon line.
First, he got a compass needle, which Rollo's father had lent him, and
put that down upon the barn floor just at the foot of the door post, and
observed the direction; and he also