600 



REPORT OF NATIONAL MUSEUM, 1904. 



During the years 1871 to 1876 work under essentially the same con- 

 ditions was continued by the Hayden survey throughout Colorado, the 

 appropriations being $75,000 annually, with the exception of 1876, 

 when they dropped to $65,000. The individual work of Hayden him- 

 self becomes gradually less conspicuous in 

 the reports issued, owing to the increased 

 amount of administrative work. 



In 1874 the party under direction of 

 A. K. Marvine was engaged in the southern 

 portion of North Park; that under Dr. 

 A. C. Peale in the region bounded on the 

 north by the Eagle and Grand rivers, on 

 the east by the one hundred and seventh 

 meridian, on the west by the State line, and 

 on the south by latitude 38° 20'. The third 

 division under A. D. Wilson, with F. M. 

 Endlich, geologist, was assigned to what is 

 known as the San Juan district, and the 

 fourth, under the immediate direction of 

 H. Holmes as artist and geologist, to the 



Albert Charles Peale. 



Doctor Hayden, with- \X 

 Elk Mountain region. 



In the report for 1871 Hayden devoted considerable attention to the 

 stratigraphic position of the Lignite group, a discussion of which may 

 be referred to later. Perhaps the most striking feature brought out 

 in the work of this year was that relative to the Elk Mountains. This 

 range was regarded by Hayden as a grand 

 illustration of an eruptive range, "the 

 immense faults, complete overturning of 

 thousands of feet of strata, and the great 

 number of peaks, all composed of eruptive 

 rocks." indicating to him periods of violent 

 and catastrophic action. The great thick- 

 ness of sedimentary strata which had been 

 carried to the loftiest points of the axial 

 ridge in a nearly horizontal position he 

 thought might be explained on the suppo- 

 sition that at one -time the sedimentary mass 

 rested on a floor of pasty or. semipasty 

 granite, and that the forces in the interior 

 were struggling to find vent and carried 

 upw T ard the entire overlying mass. This description is of interest 

 when taken in connection with one by Marvine the year previous as 

 showing the gradual inception of the laccolithic idea afterwards 

 worked out in detail by Holmes, Peale, and Gilbert, to which I will 

 now refer. 



FIG, 105.— Archibald Robertson 

 Marvine. 



