PREFATORY NOTE. 



Columbia College, 



New York, June 1, 1875. 



The following report was prepared for publication at the time indicated by the 

 date of my letter to Captain (now Colonel) Macomb, but the breaking out of the 

 rebellion arrested the publication of all the reports of surveys made by the Govern- 

 ment expeditions immediately previous to this event. The reports of the surveys 

 made by Lieutenant (now General) Gr. K. Warren, United States Engineers, Captain 

 (now General) W. V. Raynolds, the report of the Northwestern Boundary Commission, 

 and some others, were in this category, and much most valuable information in regard 

 to the tar West has been lost to the country and the world by the suppression of 

 these important documents. 



As attention is now again drawn to the region bordering the San Juan and Upper 

 Colorado, and several parties are occupied in exploring adjacent districts, the results 

 of the explorations made by the San Juan Exploring Expedition have acquired an 

 importance in this connection which has rendered their publication desirable. They 

 are therefore now given to the public, Although much has been learned in regard to 

 the <>eolo<>v of the country drained by the Colorado River during the last ten years, 

 and much that has ;i bearing on the subject-matter of this report, none of this lately- 

 acquired knowledge is referred to on its pages, but they are printed precisely as written 

 in I860. 



This course has been pursued as the only just and natural one. The observations 

 made fifteen years ago, if accurately made, have equal value now as then; if inaccurate, 

 it is only right that the credit of the correction of errors should belong to those who 

 make such corrections. The geological narrative now given stands, therefore, just as 

 written, and is a fair exponent of the state; of our geographical and geological knowledge 

 of the West at the date of its preparation. It is evident that to modify the report so as 

 to conform to all the conclusions more recently reached, would be to falsity the record 

 and greatly impair the independence ami value of the statements it includes. The 

 truth or error of these statements will soon be demonstrated by the extension of the 

 explorations of other parties into this field. It is but just that the credit or discredit of 

 the trial to which the report is to be subjected should belong to the writer. Knowing 

 that his work was done; honestly, and believing that it was in the main accurately done, 

 he accepts the entire responsibility of it, whether for praise or blame. 



J. S. N. 



