38 PROCEEDINGS OP THE AMERICAN ACADEMY 



The following notes were made at Station No. 4, when the mean 

 velocity of the stream was eight feet per second : — 



10 h 9'. There is a depression in surface of stream about 0.5 ft. below Sta. 



No. 3 ; and a swell at 0.85 ft. above Sta. No. 4. Distance from 



swell to depression, 1.15 ft. 

 11'. Depression 0.3 ft. below Sta. No. 4, and swell 1.3 ft. below Sta. No. 4. 



Distance, 1 ft. 

 12'. I should judge that the swell above Sta. No. 4 is about 0.02 ft. above 



the line connecting the depressions. 



The depression and swell move longitudinally, frequently about 



one-half a foot, and more rarely to the extent of replacing each 



other. 

 22'. There is continual change in height of surface, but noticeable fluctu- 

 ations come as often as three-quarters of a second, and from 0.01 ft. 



to 0.02 ft. in height. 

 34'. There is a swaying of the highest part of the stream from side to side ; 



generally from within a tenth of a foot from one side to a tenth of 



a foot from the other, but occasionally running nearer the side. 

 30'. There are times when the surface is quite even from side to side, 



and again it will vary as much as 0.02 ft. 

 3S 7 . A swell longitudinally follows this fluctuation from side to side, but 



is not a swell the full width of the stream. 

 39'. The swell seems to be a twisting of the thread of the current from 



one side of the trough to the other. 

 4F. In the cross section there is a rise of the surface on each side, and a 



rise of the thread of the stream tor a width of about 0.00 ft., and 



a depression each side of this. 



Immediately after the ahove observations, the following were made 

 at Station No. 8, in the midst of the series of eleven experiments, 

 having a mean velocity of 8.39 ft. per second. 



10 h 46'. The longitudinal distances between the swells and depressions are 



greater near Sta. No. 8 than at Sta. No. 4, but are less definite. 



The variation in height is at times as much as 0.02 ft. 

 52'. The surface of the stream is much more even here than at Sta. No. 4. 



There is no marked rise near the middle of the stream, but there 



is a swaying of the highest part of the stream from side to side 



about 0.01 ft. 

 64'. The line of air-bubbles is nearly obliterated, varying to 0.04 ft. each 



side of the middle, but most of the time remaining on the east side 



of the middle. 



Orifices in the Plane of Side. Passages normal. 



The results obtained with orifices whose edges do not vary percep- 

 tibly from the plane of the side of the trough, with passages normal to 

 this plane will first be considered. Such are found on both sides at 

 Station No. 4, on both sides at Station No. 8, and on the east side at 

 Station No. 9. 



