42 



BIG SPRING PRAIRIE. 



area to the mesophytic condition. The above represents 

 the curve if only one effort at drainage has been made. 

 If the ditches are cleaned out or deepened, new curves 

 must be accordingly introduced at the proper stage. 



If the soil takes fire after drainage, and a severe 

 burn ensues, the curve will need adjustment as follows: 



XEROPHYTIC 



MESOPHYTIC 



HYDROPHYTIC 



Figure 8. Reteogeession as Restjl,t of the Bttening of Soil. 



a to b — Advance under natural conditions. 



b to c — Advance under artificial drainage. 



c to d — Stage of settling before prairie fire. 



d to e — Retrogression as result of prairie fire. 



e to f — Advance under natural conditions. 



As before stated, the first ditches were dug about 

 1860, but by 1890 certain portions of prairie had so far 

 reverted toward former conditions that a joint county 

 ditch was petitioned for and granted by the proper an- 

 thorities of Seneca and Hancock counties. This ditch 

 was constructed in 1891 and is known as the Bower 

 Ditch as represented on Map I. 



Figure 9 gives an illustration of it some distance be- 

 pond the prairie area. The greater portion of this out- 

 let is cut through a considerable thickness of clay now 

 quite firm. The muck above it has undergone consid- 

 erable oxidation and consequent settling. This outlet 

 will furnish adequate drainage for great portions of this 

 prairie for many years to come. 



In 1897 it was found necessary to deepen the outlet 

 of the Brown Ditch at southern end of prairie. In order 



