1106 Journal of Aaricidtural Research voi. v. no. a* 
gence. For all. practical purposes, however, it may be stated that the 
discharge is not materially affected unless the notch is submerged until 
Hb is at least one-tenth of H A . When H B is one-eighth of H At the dis¬ 
charge is decreased approximately 2 per cent; when it is one-fourth, the 
decrease is approximately 6 per cent; and when it is one-third, the 
decrease is approximately 9 per cent. These percentages vary some¬ 
what with the head. 
