race the state of Illinois.

The base line for both the second and third principal meridians
commences at Diamond Island, in Ohio, opposite Indiana, and runs due
west till it strikes the Mississippi, a few miles below St. Louis.

All the _townships_ in Illinois, south and east of the Illinois river,
are numbered from this base line either north or south.

The third principal meridian terminates with the northern boundary of
the state.

The fourth principal meridian commences in in the centre of the channel,
and at the mouth of the Illinois river, but immediately crosses to the
_east_ shore, and passes up on that side, (and at one place nearly
fourteen miles distant) to a point in the channel of the river,
seventy-two miles from its mouth. Here its base line commences and
extends across the peninsula to the Mississippi, a short distance above
Quincy. The fourth principal meridian is continued northward through the
military tract, and across Rock river, to a curve in the Mississippi at
the upper rapids, in township eighteen north, and about twelve or
fifteen miles above Rock Island. It here crosses and passes up the
_west_ side of the Mississippi river fifty-three miles, and recrosses
into Illinois, and passes through the town of Galena to the northern
boundary of the state. It is thence continued to the Wisconsin river and
made the principal meridian for the surveys of the territory, while the
northern boundary line of the state is constituted its base line for
that region.

Having formed a principal meridian with its corresponding base line,
for a district of country, the next operation of the surveyor is to
divide this into tracts of six miles square, called "_townships_."

In numbering the townships _east_ or _west_ from a principal meridian,
they are called "_ranges_," meaning a range of townships; but in
numbering _north_ or _south_ from a base line, they are called
"_townships_." Thus a tract of land is said to be situated in township
four north in range three east, from the third principal meridian; or as
the case may be.

Townships are subdivided into square miles, or tracts of 640 acres each,
called "_sections_." If near timber, trees are marked and numbered with
the section, township, and range, near each sectional corner. If in a
large prairie, a mound is raised to designate the corner, and a billet
of charred wood buried, if no rock is near. Sections are divided into
halves by a line north and south,