LESSONS IN GEOLOGY. 



385 



was also run with great care perpendicular to the principal me- 

 ridian, and then lines were run parallel to the base line at inter- 

 vals of six miles on either side, dividing the ranges into townships 

 about six miles square. 



On account of the form of the earth it was necessary to estab- 

 lish correction, or secondary base lines at certain intervals. The 

 base line for Indiana and Illinois is in 38 58' 12" north latitude. 



fl) Township 2 north of range 2 east. 



(2) Township 2 north of range 1 east. 



(3) Township 2 north of range 1 west. 



(4) Township 1 north of range 1 west. 



(5) Township 1 north of range 1 east. 



(6) Township 1 north of range 2 east. 



(7) Township 1 south of range 2 east. 



(8) Township 1 south of range 1 east. 



(9) Township 1 south of range 1 west. 



The ranges are designated by number east or west of the 

 principal meridian and the townships by number north or south 

 of the base line; as shown in the above diagram. 



A township is six miles square and is divided into thirty-six 



L. S. 25 



