338 



NEW YORK STATE MUSEUM 



of the lake; (2) at an artificial channel through which water was 

 discharged at will for the benefit of the millers on the outlet; 

 and (3) through the conduit of the Rochester Waterworks. The 

 runoffs given are the sums of these several outgoes. In order to 

 determine the outflow of the natural outlet, a weir was con- 

 structed and the discharge observed at different hights of the 

 lake surface. The discharge into the artificial channel was 

 through submerged orifices of known dimensions, and has been 

 computed from standard formulas for the discharge of such ori- 

 fices, the size of the openings and the difference of level of w r ater 

 surfaces above and below being known. 



The discharge of the conduit of the Rochester Waterworks is 

 as computed from standard formulas for discharge through 

 pipes. Measurements made by the writer and others during the 

 last few years show that the computed quantities passing 

 through the conduit were not far from correct. 



Taule No. 49 — Water drawn from Hemlock lake for the water years 

 1880 to 1884, inclusive 

 [In Inches on the catchment] 



MONTH 



1880 



1881 



Mean monthly eleva- 

 tion of lake surface 



a 

 I 



i 



cS 



Rainfall less the 



water drawn 



o> 



3 



1 

 &. 



s 



0) 



H 



Mean monthly eleva- 

 tion of lake surface 



13 

 a 

 '3 

 « 



=3 



*o 

 u 



<s> 



3 



Rainfall less the 



water drawn 



9 



5 

 +■> 



s 



p. 



I 



(1) 



1 



(2) | (3) 



(4) 



(5) 



(6) 



(2) 



(3) 



(4) 



(5) 



(«) 





—1.67 1.26 



0.16 

 0.15 

 0.16 

 0.15 

 0.15 

 0.17 





tt31.4 

 a 25. 5 

 a27.3 

 o31.8 

 a45.7 

 71.8 



-1.33 

 -1.47 

 -0.11 

 +1.20 

 +1.47 

 +1.32 



0.72 

 2.24 

 1.08 

 1.92 

 0.52 

 2.23 



0.49 

 0.44 

 0.54 

 1.73 

 1.24 

 1.11 





27.3 

 24.7 

 29.7 

 39. 1 

 45.2 

 69.7 



39.3 





-0.91 

 -0.11 

 +0.21 

 +0.79 

 +0.87 



1.37 

 1.45 

 1.47 

 1.25 

 2.08 























May 













-o.u 



8.88 



0.94 



7.94 



38.9 



+0.18 



8.71 



5.55 



3.16 



+0.45 

 -0.15 

 -0.70 



1 66 



0.36 





76.5 

 77.1 

 74.4 



4-1.08 3.13 



0.76 

 0.43 

 0.50 





73.9 

 75.6 

 80.0 



July 



1.93 0.41 

 3.46 0.35 





+0.58 



3.71 

 0.95 

















6.10 



-0.13 



7.05 1.12 



5.93 



76.0 



+0.55 



7.79 



1.69 



76.5 



-1.13 



1.35 0.31 





69.7 

 53.4 

 37.1 



-0.69 

 -0.81 

 -0.71 



1.73 

 4.23 

 1.81 



0.35 

 0.33 

 0.46 





77.9 

 59.1 

 44.8 



60.6 





-1.57| 3.85 0.31 

 — l.M| 0.8G 0.39 











Replenishing period 





-1.31 6.06 1.01 



5.05 



53.4 



-0.74 



7.77 



1.14 



6.63 



—0.431 21.99 3.07 



1 1 1 



18.92 



51.8 



+0.04 



24.27 



8.38 



15.89, 53.9 



a Interpolated from average of fifteen years 



