finished topography. In connection with this, 1,932 miles of spirit levels were run and 100 permanent bench marks were established. Portions of the southern border of the State were surveyed in connection with the filling out of quadrangular areas in Maryland and West Virginia by the co-operative topographic surveys of those States. The work near the Maryland boundary was under the general charge of Mr. W. Carvel Hall, topographer, assisted by Messrs. A. C. Roberts, topographer, and W. N. Brown, assistant topograher. This party mapped fifty-two square miles on the northern edge of Blair and Parkton quadrangles, in York county. The work near the West Virginia boundary was under the general direction of Mr. A. M. Walker, topographer, aided by Mr. J. M. Whitman, Jr., field assistant. This party completed the mapping of twenty-six square miles on the northern edge of Morgantown quadrangle, in Greene and Fayette counties.

The detailed results of the spirit levels run in the course of the above work, including descriptions and elevations of all permanent bench marks set, is set forth in Appendix D, pages 113-135 of this report.

The following tabular statements show in detail the various facts connected with the topographic mapping of the two seasons. This shows the amount of instrumental control on which the maps are based and the total cost of each portion for all field work, including salaries in the field:

SPIRIT LEVELING.

Under the various topographers parties were engaged in running spirit levels in the areas being surveyed in 1899 and parties during the year 1900. The object of this leveling was to determine elevations and establish bench marks upon which to base the contour sketching of the area mapped. These elevations are all reduced to mean sea level. In the process of this work there were run 2,458 miles of levels, during which there were established 153 permanent bench marks of bronze or aluminum and 12,063 other elevations were determined. Including trigonometric elevations there were determined an average of four instrumental elevations for the control of each square inch of map. Many more elevations were determined by methods of less accuracy.

PLANETABLE AND TRAVERSE CONTROL.

Horizontal control was established in the progress of topographic mapping by planetable triangulation and road traverse. The positions of 4,254 points were accurately determined by trigonometric methods, the elevations of which were ascertained at the same time and in the same manner. There were also run 14,303 miles of road traverse. The horizontal control of the maps averaged approximately one trigonometric location per square inch of map and 35 linear inches of platted road traverse per square inch of map.

LAND CLASSIFICATION MAPS.

As a result of the land classification indicated on the topographic field sheets, there has been prepared in manuscript complete woodland maps of the areas surveyed. Upon these is indicated by colors. and by numbers the various facts recited in the following instructions of the Director of the United States Geological Survey:

1. All lands hereafter mapped in the course of topographic surveys will be classified as (1) woodland, (2) pasture or grass land, (3) cultivable land, (4) waste or desert land.

2. Woodland will be subclassified as (a) merchantable timber; (b) tracts containing trees so small in size or of such quality as not to be valuable for lumber, but which may be used for fence posts, firewood, etc.; (c) brush, such as chaparral; (d) burnt areas.

3. Natural pasture or grass land will be subdivided into two varieties: (a) such as may be used for pasturage or cut for hay; (b)