OP ARTS AND SCIENCES. 31 



During experiments with mean velocities less than three feet per 

 second, the trough was maintained in its level position, and the height 

 of surface and velocity were regulated by screwing a steel plate to the 

 lower end of the trough at the proper height, thus discharging the 

 water over a weir. With greater velocities, the plate was removed, 

 and the trough was more or less inclined. 



During experiments, the measurement of the quantity of water 

 flowing through the trough was continuous, interrupted only by draw- 

 ing water from the measuring basin. 



Generally there were as many as four observers, with their instru- 

 ments, making simultaneous observations at as many stations, with 

 assistants to record their reading. 



Upon experimenting with velocities greater than three feet per 

 second, the disturbance at the entrance was found to continue past 

 Station No. 1, consequently all the observations at this station are 

 omitted. 



At stations numbered from two to ten inclusive, 5925 observations 

 were made upon the height of the different water surfaces, with veloci- 

 ties in the trough from about 0.6 ft. to about 9 ft. per second. These 

 observations have been divided into 518 experiments, giving a series 

 of heights in each still-box above the surface of the stream at the 

 respective stations. These experiments have been grouped, by put- 

 ting together those at each station in which the mean velocity and 

 depth of water in the trough were nearly constant, and taking the 

 mean of the heights of the water in each still-box above the surface 

 of the stream. These mean results for each velocity, together with 

 the depth of water, the number of observations, and number of experi- 

 ments included in each result, are given in the following tables, and 

 are followed by columns of corrected results, which are described in 

 the headings : — 



