208 THE HYDROGRAPHY OF PR12«rCE GEOKGE's COUXTY 



is often rock, sometimes overlaid with a thin layer of gravel, and 

 the fall is quite rapid. There are several important power develop- 

 ments, notably at Lanrel and Guilford. At Laurel a total of about 

 260 horse-power is used, wdiich can generally be obtained during 

 only 9 months, or less, of the year. Of these, 60 horse-power are 

 used in the Avondale Flour !Mill and the remainder in the Laurel 

 Cotton Factory. 



THE PATUXEXT RIVER AT LAUREL. 



This station, which was established August 3, 1896, on the bridge 

 on the main cross street of the town of Laurel, ]\Id., was discontinued 

 AugTist 10, 1898. The initial point for soundings was the end of 

 iron truss on the upstream side of the bridge. A wire gage with 

 metal w^eight was attached to the lower side of the bridge, the scale 

 being a 14-foot board spaced to tenths of a foot with small nails, and 

 fastened to the floor timber of the bridge. The bench mark is a 

 copper bolt set in a large capstone of the retaining wall on the lower 

 side of the bridge abutment on the left bank of the stream. It is 

 21.22 feet above zero of gage height. The drainage area is 137 

 square miles. The flow of water past this station at low stages of 

 the river is confined to certain hours of the day, on account of the 

 influence of the dam at the large cotton mill situated about 1 mile 

 up the stream from the station. 



In the following table are the results of the several current meter 

 measurements of the quantity of water flowing past this station in 

 cubic feet per second at various stages of the river. Each of these 

 measurements has been plotted as a point on cross-section paper, 

 using gage height and discharge as coordinates and a smooth curve, 

 called the rating curve, has been drawn in such a position as to 

 average in a general way the inconsistencies and inaccuracies of 

 these points. The rating curve shows the probable discharge of the 

 river at any gage height, and from it has been made the rating- 

 table which follows the table of discharge measurements. The reconl 

 of daily gage height shows the fluctuations of the river from day 

 to day, and when applied to the rating table enables one to estimate 

 the daily discharge of the river. The estimates of dailv discharge 



