



PROFESSIONAL PAPERS OF THE ENGINEER DEPARTMENT, U. S. ARMY. 



No. 18. 



IlEP»OIlT 



OF THE 



GEOLOGICAL EXPLORATION OF THE FORTIETH PARALLEL 



MADE 



BY OEDEE OF THE SECEETARY OF WAR ACCORDING TO ACTS OF 

 CONGRESS OF MARCH 2, 1867, AND MARCH 3, 1869, 



TJNDEK THE DIRECTION OF 



BRIG. AND BYT. MAJOR GENERAL A. A. HUMPHREYS, 



CHIEF OF ENGLNEEE8, 



BY 



CLARENCE KING, 



U. S. GEOLOGIST. 



