father, he could make the mark right along quick."

"No matter how quick he might make it. It would take some time, wouldn't
it?"

"Only a _very little_," said Rollo.

"And do you suppose the sun would stand still, even during that little
time, so as to let the shadow remain stationary?

"However," continued his father, "I don't say this to disparage Jonas's
noon mark. I dare say, it is accurate enough for his purposes. He only
wants to know from it when it is time for him to come in to dinner, or
something like that. I only want you to understand what exactness is,
and to see, a little, how difficult it is to attain to any considerable
degree of it, in such cases. So thus, it seems, that Jonas has got a
sort of a dial?"

"Why, it only tells him what o'clock it is at one hour in the day,"
said Rollo. "But I think he might make it do for all the afternoon and
forenoon."

"How?" inquired his father.

"Why, all he has got to do is to watch some day when it is nine o'clock,
and ten o'clock, and so on, every hour; and then make a line where the
shadow comes every hour, just as he did for twelve o'clock. Then he will
have marks for every hour in the day, and when the shadow comes along to
these marks, one after another, he will know what time it is."

"O, but the difficulty is," said his father, "that the shadow will not
come to the same places, at the same hours, on different days. It will
come to the _meridian line_, at twelve, always,--that is, nearly to it;
but it will not come to any other lines regularly,--that is, if the
object, which casts the shadow, is upright."

"Will any other kind of object carry the shadow regularly?" asked Rollo.

"Yes," said his father, "an object that leans over to the north, so as
to point to the North Star. If you and Jonas could put a post into the
ground so as to have it point to the North Star, then you could mark,
all around it, the places to which the shadow would come for every hour
in the day, and afterwards it would come to the same places regularly,
or nearly so. It would be near enough for your purposes; and I don't
know but that it would be quite a respectable dial for you."

Rollo then asked his father why it was that a post, which pointed to the
North Star, would bring a shadow any more regularly to the hour marks,
than an upright one would; but he said that Rollo did not know enough,
yet, to understand the explanation, even if he were to try to explain
it. "There