1(J8 GEOLOGY OF ILLINOIS. 



lauds. Big Bureau creek comes in from Lee county rear the north-east 

 corner of Bureau. It flows in a general south-west direction to a point 

 a short distance west of the city of Princeton ; from thence it takes a 

 south course for ten or twelve miles, and then turns nearly due east and 

 falls into the Illinois river some five miles from where the south boundary 

 line of the county strikes that river. This stream has very little alluvial 

 bottom land along its course. The prairie rises in rather abrupt swells 

 from the banks of the stream. About Tiskilwa and on to the Illinois 

 river there is an alluvial bottom, covered with a dense growth of timber. 



West of Little Bureau creek is a tributary of the former, rising in the 

 northern part of the county and forming a junction with the larger 

 stream a few miles south-west of Princeton. It is a smaller stream, but 

 of the same general character. 



Brush creek and Coal creek are small prairie streams, the latter flow- 

 ing near Sheffield, and losing itself in the Green river swamp land. 



On the south-east corner of the county, the Illinois river forms the 

 boundary line for a distance of some fifteen or sixteen miles. There is 

 a broad alluvial bottom along this river on the Bureau county side. 

 The lowest bottom is mostly a swampy, grassy plain, interspersed with 

 sloughs, and ridges of river sand, and subject to inundations when the 

 Illinois river sends out its floods over the low banks. One of these 

 sloughs assumes the character of a lake, communicating with the Illinois 

 river at its southern terminus. The town of Trenton is built upon the 

 west side of this lake, half a mile or more from its outlet into the river. 

 At ordinary or high stages of water, steamboats enter this lake slough, 

 and make their regular landings at Trenton. I shall have more to say 

 of this valley when describing the geological formations of the county. 



Timber. Along Green river there are a few scattering bunches of 

 rather scrubby timber. Big Bureau has a scattering belt along its mar- 

 gin for a considerable portion of its course above Princeton. Below 

 that city it enters a timbered region. The townships of Princeton, In- 

 dian Town, Arispe, Lepertown, Selby, and Hall, in the south and cast 

 portions of the county, all have considerable tracts of timber. Those 

 below Tiskilwa, and bordering the Illinois river, are bluffy, and mostly 

 covered with a scattering growth of such trees and brush as may be 

 found in similar localities in the northern part of the State. 



Big Bureau Grove, in the western part of the county, has a consider- 

 able body of timber. 



Crow creek, in the township of Milo, and Pond creek, west of Tis- 

 kilwa, two small streams not named above, have each some scattering- 

 trees along their courses. 



"Dad Joe's Grove," in the north-western part of the county, is a small 

 grove on a very high elevation, and is a conspicuous land-mark for a 

 long distance over the prairies. 



