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INTRODUCTION. 
I have placed in this volume several reports and memoirs relating to American Geology that | 
have appeared already in different scientific publications during the years 1855 and 1856. ! 
The first tvim reports were published in 1855 at Washington in the Documents accompanying 
the Report of the Secretary of War on the several Pacific Railroad explorations , edition in OCtavo. These jj 
two reports are extremely concise and merely provisory, intended to be replaced by full and final 
reports on the geology of the routes explored by Captains A. W. Whipple and John Pope. An 
abuse of authority on the part of the Secretary of War, Mr. Jefferson Davis, took from me the pre- j 
paration and publication of these final reports, and I here declare that I know nothing of the publi- 
cation of the edition in quarto of these reports, and that 1 decline all responsibility as to the use , 
that may have been or may hereafter be made by others of my official note-books, and of the 
specimens that I collected. j 
In the month of May 1853 I was appointed United States Geologist , with orders to join the 
Expedition, commanded by Capt., then Lieut. Whipple, at Napoleon, Arkansas, in order to ex- : 
plore the route near the 35"' parallel of latitude. This long and difficult journey from Boston to 
San Francisco passing by Cincinnati, Ohio; Napoleon and Fort Smith, Arkansas; Albuquerque 
and Santa Fe, New Mexico; and the Pueblo de los Angeles, in California, occupied nearly a year j 
from the 2'> June 1853 to the 26“' JIarch 1854. In returning from California by the Isthmus of Pa- 
nama , I was attacked by sickness of a serious nature , quite frequent in that unhealthy climate , a 
chronic diarrhoea; and on my arrival at Washington, the 1*‘ June 1854, I stated my desire to 
pass the winter in Europe on account of my health, which had been much injured by the fatigues 
and exposures of this long journey across a wilderness. The American Government made no ob- 
jection to this project of a voyage to Europe, on the contrary I was told that I should be better 
prepared to make a complete and detailed report, having at my command the resources of Euro- 
pean Science. Captain Whipple only asked me to make a geological Resume for the octavo edition, 
and I did so notwithstanding the state of complete prostration to which I was then reduced by my 
malady. 
Early in September , my health beginning to improve , I received from Captain Pope (who 
had arrived at Washington, from his exploration of the route near the 32'‘ parallel of latitude, 
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