Marshall, R. B.  1867-1949. <br/><br/>
Results of spirit leveling in Illinois, 1909 and 1910 / 
R.B. Marshall, chief geographer. Work done in cooperation with the state of Illinois. 
 - Washington,  Govt. Print. Off.,  1911. 
 - 115 p. :  pl. ;  24 cm. 
 - U.S. Geological survey. Bulletin 493 .
 - United States.  Geological Survey.  Bulletin ;  493. .
<br/><br/> Includes index. 
<br/><br/><label>LCCN: </label>gs 11000616  
<br/><br/><label>Subjects--Geographic Terms: </label><br/>Illinois--Altitudes.
<br/><br/><label>LC Class. No.: </label>QE75  / .B9 no. 493