MARYLAND GEOLOGICAL SURVEY 275 



vania there are still immense tracts of forest lands. At flood height 

 the river may rise 30 feet, while the minimum flow of the stream is 

 small, as may be seen from the records of discharge on the follow- 

 ing pages. 



In the Tenth Census of the United States, volume xvi, may be 

 found data upon the fall of the tributaries and main Susquehanna, 

 and a record of waterpowers developed and undeveloped. 



A systematic study of the flow of the Susquehanna has been made 

 since 1890 by the U. S. Geological Survey, the point of measurement 

 being at Harrisburg, Pennsylvania. Observations of the height of 

 water in the river were made several years previous at the pump- 

 house of the waterworks located in the western part of the city of 

 Harrisburg, and these records have been continued to date and fre- 

 quent current meter measurements made by hydrographers of the Sur- 

 vey. The gage is located in the pump well, which is directly con- 

 nected with the river by means of large water mains. A float in this 

 well is attached to a cable and counterweight, the height of water 

 being indicated upon a painted scale. The datum is the low water 

 mark of 1804. Observations are made by the engineer, Mr. C. M. 

 Nagle, each morning before starting the pumps. The records have 

 been furnished since 1890 through the courtesy of Mr. E. Mather, 

 President of the Harrisburg Waterworks Company. 



Measurements of discharge are made by the method previously de- 

 scribed, from an open iron bridge on Second Street, the initial point 

 of sounding being the iron upright at the east end of the bridge. The 

 channel at and below the station is straight for about 2500 feet, the 

 banks being high and the current of moderate velocity. The stream at 

 this point is divided into two channels with a, large island between, and 

 at the time of lowest water it has been found advantageous to meas- 

 ure the right-hand channel by wading. The first measurement was 

 made on March 30, 1897, by Mr. E. G-. Paul. The record of gage 

 heights and the results of measurements at Harrisburg are here given. 

 Also the computation of flow by months. 



