every hour.

"Suppose then it takes the sun one hour to go from us to the river
Mississippi, how many degrees west of us, would the river be?"

Having thus familiarized the pupils to the fact, that the motion of the
sun is a proper measure of the difference of longitude between two
places, the teacher must dismiss the subject, for a day, and when the
next opportunity of bringing it forward occurs, he would perhaps take
up the subject of the sun's motion as a measure of _time_.

"Is the sun ever exactly over our heads?"

"Is he ever exactly south of us?"

"When he is exactly south of us, or in other words, exactly opposite to
us, in his course round the earth, he is said to be in our meridian. For
the word meridian means a line drawn exactly north or south from any
place."

There is no limit to the simplicity which may be imparted, even to the
most difficult subjects, by subdividing the steps. This point for
instance, the meaning of meridian, may be the subject, if it were
necessary, of many questions, which would render it simple to the
youngest child. The teacher may point to the various articles in the
room, or buildings, or other objects without, and ask if they are or are
not in his meridian. But to proceed:

"When the sun is exactly opposite to us, in the south, at the highest
point to which he rises, what o'clock is it?"

"When the sun is exactly opposite to us, can he be opposite to the Rocky
Mountains?"

"Does he get opposite to the Rocky Mountains, before, or after, he is
opposite to us?"

"When he is opposite to the Rocky Mountains, what o'clock is it there?"

"Is it twelve o'clock here, then, before, or after it is twelve o'clock
there?"

"Suppose the river Mississippi is fifteen degrees from us, how long is
it twelve o'clock here, before it is twelve o'clock there?"

"When it is twelve o'clock here then, what time will it be there?"

Some will probably answer "one," and some "eleven." If so, the step is
too long, and may be subdivided thus:

"When it is noon here, is the sun going towards the Mississippi, or has
he passed it?"

"Then has noon gone by, at that river, or has it not yet come?"

"Then will it be one hour before, or one hour after noon?"

"Then will it be eleven, or one?"

Such minuteness and simplicity would, in ordinary cases, not be
necessary. I go into it here, merely to show, how, by simply subdividing
the steps, a subject ordinarily perplexing, may be made plain. The