During the progress of the survey the outcrop of the coal was determined with great care, and the resulting maps will doubtless be the best general maps yet published.

From surface indications and mine and well data the depth of the Pittsburg coal beneath the surface was approximately determined wherever the coal is below the surface of the ground. The position of the coal bed will be shown on the published maps by means of contour lines drawn on the floor of the coal, so that not only is the depth of the coal represented, but also its dip and the form of the basin in which it occurs.

In the region east of Chestnut Ridge, the Upper Freeport coal is the most important economic feature, and this is treated in much the same manner as the Pittsburg coal in the region just described.

All other coal outcrops were examined as carefully as circumstances would permit in order to determine what portions of the field and what coal beds would be available for fuel production when the Pittsburg bed is exhausted. This contingency is not expected to occur in the near future, but undoubtedly it is only a question of time when other coal beds will be called into requisition to meet the constantly increasing demand.

The area surveyed geologically in this part of the State amounts to 458.5 square miles. The data obtained in this survey has been prepared in the office of the United States Geological Survey for publication in folio form on maps of the scale of 1 inch-1 mile, approximately. This is now being printed and probably will be issued to the public about April 1, 1902.

The geological survey of the Uniontown and Masontown quadrangles was completed by the last of August and on the first of September the party moved to the northern part of the State and began the survey of the Gaines and Elkland quadrangles. These cover an area of 445 square miles, located in the counties of Potter and Tioga.

The geology of this region is greatly obscured by drift brought by glacial ice from the north, consequently a specialist in this branch of geology, William C. Alden, was added to the party. Mr. Alden began work September 22, and gave his entire attention to the study of the glacial deposits.

In mapping the obscure Devonian formations in these quadrangles, it was found desirable to have a paleontologist in the field, whose duty it would be to collect and study fossil forms and to assist the geologist in tracing and identifying the formations. Charles Butts has been engaged in such paleontologie work in southern New York for several years, and, on account of his familiarity with the geology and paleonotology of this region, he was engaged as collector and

general assistant. He began work about September 1, and remained until the close of the field season.

During the progress of the survey of these quadrangles, it was found that the topographic maps did not include the Gaines oil field, which has lately developed on the south side of Pine creek, near the town of Gaines, in Tioga county. In order that a geologic report of this field might be prepared in conjunction with the report on the Gaines quadrangle, Mr. H. M. Wilson was requested to prepare a topographic map of the oil field upon which to base. a geologic report. Mr. Fuller made an examination of this field in order to determine the position of the oil sands, the relation of the pools to the anticlinals and synclines of the region, and the possible future extension of the productive territory. The results of this study have been embodied in a short paper which will appear in the Twenty-second Annual Report of the Director of the United State Geological Survey.

The areal work in these quadrangles was finished on September 30, and Messrs. Campbell, Irving and Fuller left the field on that date. Mr. Alden remained throughout the month of October, engaged in mapping the glacial formations, and Mr. Butts was employed until October 24, in collecting fossils from critical localities.

The geologic work on these quadrangles involves some disputed questions concerning the rocks of northern Pennsylvania; therefore, the geologist in charge considered it inadvisable to attempt their publication in folio form during the winter of 1900-1901, but he has promised to prepare all of this material for publication at the close of the next field season.

The geologic data which has been collected during the progress of this co-operative survey is on file in the office of the United States Geological Survey, and it is available at any time for separate publication by the State in such form as is deemed most desirable.

PRIMARY TRIANGULATION AND TRAVERSE.

During the field season of 1899 there were at work between the months of May and November seven parties, under the charge, respectively, of Messrs. S. S. Gannett, topographer; A. H. Thompson, geographer; Sledge Tatum, topographer; Oscar Jones and Walter R. Harper, assistant topographers, and E. L. McNair and D. H. Baldwin, field assistants. During the months of September and October, Mr. W. Carvell Hall, topographer, was in charge of a party running primary traverse over four lines of railway between Baltimore, Md., and York, Pa. This traverse controlled in Pennsylvania an area of 500 square miles, included in two quadrangles.

In addition to directing and supervising the work of the other triangulators, Mr. S. S. Gannett measured a primary base on the

line of the Pennsylvania Railroad near Hillside and occupied numerous stations in the areas in which the various parties were working, either in the course of the supervision of their work or in conjunction with them.

Prof. A. H. Thompson was engaged in extending triangulation in the general neighborhood of Indiana and Greensburg; Mr. E. L. McNair, between Indiana and Clarion; Mr. Walter R. Harper, between Uniontown, Greensburg and Pittsburg; Mr. D. H. Baldwin, between Beaver and Pittsburg; Mr. Sledge Tatum, between Morgantown, W. Va., and Uniontown, Pa., also between Chambersburg, McConnellsburg, Everett and Altoona; Mr. Oscar Jones, between Elmira, N. Y., and Tioga, Bloomsburg and Williamsport, Pa.

The gross results of the field work of these parties was the occupation and monumenting of ninety-eight separate stations, the establishment of nine meridian marks, at as many county seats, and the furnishing of primary control for 7,500 square miles, included within the limits of 33 15' quadrangles. These cover portions of the following 17 counties, namely: Erie, Tioga, Potter, Lycoming, York, Franklin, Fulton, Bedford, Fayette, Greene, Washington, Westmoreland, Indiana, Armstrong, Clarion, Allegheny, Beaver.

During the entire season of 1900, Messrs. Thompson and Baldwin were in charge of parties engaged in extending primary triangulation in the central and western portions of the State. Mr. Tatum was engaged in similar work in western Pennsylvania during portions of April and May, and Mr. Gannett during portions of August and September. The result of the field work of these parties was the occupation and monumenting of 47 stations, which furnished primary control for 15 15' quadrangles. These cover portions of the following ten counties: Adams, Cumberland, Bedford, Blair, Cambria, Huntingdon, Greene, Washington, Allegheny and Beaver. In addition, one meridian was marked by posts at Washington county seat, and the Westchester quadrangle was controlled by fifty miles of primary traverse by Mr. Tatum in March, 1901.

The detailed results of the office computation of primary triangu lation and traverse are set forth in Appendix B, page 37, which contains descriptions of each station, with its final latitude, longitude and other essential geodetic data.

Precise Leveling. During the months of May, June and July, 1899, Mr. E. L. McNair, and during the months of September, October and November, Mr. C. H. Semper, ran lines of precise levels as follows: From a bench mark of the United States Coast and Geodetic Sur vey transcontinental levels at Grafton, W. Va., via Uniontown and Brownsville, Pa., to Pittsburg; also, from a bench mark of the precise levels of the United States Geological Survey at Redhouse,

near Salamanca, N. Y., via Warren, Oil City and Franklin, Pa., to Pittsburg; also, from a bench mark of the United States Engineers, at Erie, Pa., via Meadville to Franklin; also, from a bench mark on the line of precise levels of the United States Geological Survey, near Elmira, N. Y., over the Northern Central Railway to Williamsport. At Pittsburg connection was made with the bench marks of the precise levels of the Pennsylvania Railroad, thus giving practically four independent checks on the elevation of the Pittsburg datum, all of which agreed within a remarkably small limit of error. At Williamsport connection was made with the precise levels of the Pennsylvania Railroad and the difference of elevation found was transferred to the bench mark of the Pennsylvania Railroad precise levels at Harrisburg, and connection made between this and the bench mark of the United States Coast and Geodetic Survey precise · levels, thus determining the elevation of the Harrisburg datum by four separate routes of levels, two of these being by different lines of the Coast Survey. All of the precise leveling executed by the Geological Survey comprised the running of 533 lines of duplicaterodded lines and the establishment of 96 permanent bench marks.

The details of the closures of this work on the lines of precise levels of the other organizations named are published on pages 113135, in Appendix D, to this report.

Topographic Surveying.-There were maintained on this work dur ing portions of the season of 1899, six parties. Mr. Frank Sutton, topographer, was placed in general charge of a group of three par ties, headed by himself and Messrs. R. D. Cummin and A. C. Roberts, topographers. During the season these parties completed the mapping of four quadrangles-the Erie, Girard, Uniontown and Masontown, in Erie, Crawford, Fayette and Greene counties. In addition, they completed the control of a portion of the mapping of the Brownsville and Connellsville quadrangles, in Fayette, Washington and Westmoreland counties. During the months of July, August, September and October Mr. J. H. Jennings, topographer, assisted by Messrs. J. H. Wheat and J. W. Thom, topographers, and Mr. A. H. Bumstead, assistant topographer, completed the mapping of the Elkland and Ganies quadrangles, and the control of the Tioga and a portion of the Antrim and Mercersburg quadrangles, in Tioga county. Mr. Sutton's parties commenced field work early in April, and were disbanded early in November. The area surveyed was mapped to a scale of 1:62,500, with a contour interval of 20 feet, and aggregated 1,257 square miles of finished topography. In connection with this line 526 linear miles of spirit levels were run and 53 permanent bench marks were established.

Portions of the southern border of the State were surveyed in connection with the filling out of quadranglar areas in West Virginia

and Maryland. This work was in charge of Mr. W. Carvel Hall, topographer, assisted by Mr. W. N. Morrill, assistant topographer, and various temporary aids. In all, there were thus mapped fiftytwo square miles on the northern borders of the Hancock and Havre de Grace quadrangles, in Fulton, Franklin, Lancaster and Chester counties.

During portions of the season of 1900 seven parties were maintained on this work. Mr. Frank Sutton, topographer, was placed in general charge of a group of three parties, headed by Messrs. J. H. Wheat, topographer; T. G. Bassinger, assistant topographer, and himself. Messrs. W. N. Morrill and A. C. Roberts, topographers, spent the months of May and June on the same group of work under Mr. Sutton's direction. During the season these parties completed the mapping of four quadrangles-Indiana, Latrobe, Connellsville and Brownsville-covering portions of Indiana, Westmoreland, Fayette, Washington and Allegheny. They also completed the control and partial mapping of the Waynesburg, Beaver, Rural Valley and Eldersridge quadrangles, covering portions of Greene, Beaver, Allegheny, Armstrong and Indiana counties. Mr. W. L. Miller, topographer, spent the months of May, June, July and August, and Mr. W. C. Hall, topographer, the month of September in charge of a party which completed the mapping of the Kittanning quadrangle, covering portions of Armstrong, Butler and Clarion counties. Mr. R. D. Cummin, topographer, spent the season in charge of a party which completed the mapping of the Mercersburg and Chambersburg quadrangles, covering portions of Fulton and Franklin counties; also, the control and partial mapping of the Carlisle quadrangle, covering portions of Cumberland, York and Adams counties. Mr. A. M. Walker, topographer, completed the mapping of the Everett and Tioga quadrangles, covering portions of Bedford and Tioga counties, and the mapping of part of the Hollidaysburg quadrangle, in Blair, Huntingdon and Bedford counties. Mr. Hersey Munroe, topographer, was engaged throughout the season, assisted during the months of September, October and November by Mr. W. R. Harper, assistant topographer, in completing the mapping of the Wernersville, Slatington and Boyertown quadrangles, covering portions of Lebanon, Berks, Lancaster, Northampton, Lehigh, Bucks and Montgomery counties; also, the partial mapping of the West Chester quadrangle, covering portions of Chester, Delaware and Newcastle counties. Mr. Glenn S. Smith, topographer, spent the month of October in mapping a small portion of the Galeton quadrangle, in Tioga and Potter counties.

The area surveyed was mapped to the scale of 1:62,500, with a contour interval of 20 feet, and aggregated 2,760 square miles of