MACON COUNTY. 191 



dark clay, vegetable mould and a little sand. On the gravelly shoals 

 many small shells are often found, belonging to the genera Paludina, 

 Melania, Cyclas and Unio ; where the water is more sluggish Anodontas 

 are common. 



On the flat prairies there are many small marshy tracts, fresh plow- 

 ing of one of them disclosed to view remains of old shells of the genus 

 Planorbis and Lymnea. It is not improbable that in a few years most 

 of these ponds or marshes will be drained and cultivated, and the 

 calcareous material of the shell remains will be found a useful addition 

 to the productiveness of the soil. 



Drift. — At Decatur there appears 6 to 10 feet of mostly yellowish- 

 brown clay, then similar clay with bowlders and pebbles extending 

 downwards several feet, then blue and brown clay and pebbles. 



On Big creek, in sec. i, T. 15 N., E. 3 E., the drift appears thus : 



1. Thirty feet of drift clays "with loose pebbles, sand and clay ; at lower part comminuted sand and 



clay. On the lower slope of this is an abundant growth of Equisetum or scouring rush, associated 

 with Gentiana alba and Pedicularis lanecolata. 



2. Eight feet. The upper part dark brownish-black; lower part black and apparently of vegetable 



origin, no pebbles seen; when struck a hollow sound is produced. Debris from above falling 

 over unites with this, forms a marshy talus, on which were growing Lobelia syphilitica., Sayittaria 

 variabilis and several other marsh plants. 



The above drift section is very similar to an outcrop on Whitley's 

 creek in Moultrie county. 



Bowlders and pebbles of granite, quartzite, altered sandstone, 

 porphyry, limestone, chert, etc., are found alougthe streams and irregu- 

 larly scattered on the prairies, aud sometimes very large ones are found 

 alone on the flat prairie. Three miles south of Oakley observed a 

 bowlder of gray granite of an irregular shape, measuring 8 feet across 

 in two directions, and sticking up 1 feet above the ground. The sur- 

 rounding soil is rich and black and no other bowlders were seen near by. 



Wells. — At the railroad depot, Decatur, Mr. Isaac 0. Pugh informed 

 me that a well had been dug 90 feet deep through saud aud gravel, but 

 no permanent stream of water was reached. Mr. Pugh's well . is 35 

 feet deep and affords plenty of water. 



On the flat prairie south of Decatur water is found at a depth 13 feet. 



Near the east county line, south of the railroad, it is reached at from 

 12 to 57 feet, but the supply fails in dry seasons ; but at 27 to 40 feet 

 fine streams are generally obtained, occurring in beds of sand beneath 

 the blue clay. In the north-east part of the county water is obtained 

 at from 10 to 20 feet from the suriace, and near Forsyth from 16 to 30. 

 On the rolling prairies in the western part of the county, water occurs 

 at very irregular depths. 



Harristown is located on what seems to be an elevated prolongation 

 of a low drift ridge. At this place a well was dug through 10 feet of 

 yellow clay, then 70 feet of blue clay with no sand, and only surface 



