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, and into quarters by a transverse line. In sales under certain conditions, quarters are sold in equal subdivisions of forty acres each, at one dollar and twenty-five cents per acre. Any person, whether a native born citizen, or a foreigner, may purchase forty acres of the richest soil, and receive an indisputable title, for fifty dollars.
