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and prepared at once to resume field work in my own district. Your general instructions to "complete the survey of the Central Mineral Region, including the outlying pre-Carboniferous strata, and such exposures of the Carboniferous as may lie within this area or adjacent to the same upon the east and south," have been carried out as fully as possible in the limited time which could be allowed for the work. The field has now all been explored, by far the greater part in sufficient detail for the construction of a geologic map; but as the area is very much greater than we had supposed, and the facilities for travel in the dry season are rather limited, I have been unable to present a report which can be regarded as final in any permanent sense. We were in the field but three months this year, as against five months in 1889. With a larger party, the equipment was reduced from motives of economy, rendering the executive duties more onerous and giving less available time for the geological work.

The field party was organized as follows:

• Theo. B. Comstock, in charge.
• J. C. Nagle, Topographer.
• Charles Huppertz, Geological Aid.
• H. B. Jones, Compassman.
• J. F. Clark, Contact Runner.
• H. H. Harris, Rodman.
• R. A. Thompson, Rodman.
• Harry Foster, Hostler.
• Frank Tuttle, Cook.

Upon the return from the field, September 2, the party was disbanded, Mr. J. C. Nagle and Mr. R. A. Thompson being retained for office work. Mr. Thompson left me to attend the University before the end of September, and soon after Mr Nagle received well merited promotion to the responsible charge of the Department of Civil Engineering and Physics in the State Agricultural and Mechanical College. Mr. Frank S. Ellsworth, at present engaged as general assistant, began work October 23, 1890. Mr. G. V. Skelton has been employed since December 5 as draughtsman.

The region traversed the past season is very largely made up of Silurian rocks at surface, and these afford comparatively few economic minerals, but we have been able to trace out the principal ore belts and to study the limits of the fields in which the mineral resources abound. The map which accompanies my report for 1890 gives all details of structure and distribution which have been collated to date.

The method of survey adopted has been somewhat different from the plan followed in 1889, but in essential features it is the same. Each day's work was arranged by myself, the topographers, field assistants and camp men