Haughton and Reynolds — " Drag " of Water upon Water. 285 

 The mean of the three observations with single readings is, 



1 



/ = 



305-88' 



and the mean of all the ohserTations made with amplitude 6o, nearly 

 100°, is 



f 



1 



308-50 



5. %th July, 1879. — Observed by Dr. Macalister and self, using 

 double readings with both indices : — 



n 



e 



Combination. 



I 



7 







346°-500 



(0, 15) 



307-0 



1 



298 -000 



(0, 1) 



310-7 



2 



253 -250 



(0, 2) 



298-9 



3 



missed 





— 



4 



186 -500 



(0, 4) 



302-5 



5 



158 -670 



(0, 5) 



299-7 



6 



136 -870 



(0, 6) 



302-3 



7 



116 -750 



(0, 7) 



301-5 



8 



100 -620 



(8, 13) 



306-7 



9 



86 -250 



(5, 9) 



307-4 



10 



74 -250 



(5, 10) 



308-7 



11 



63 -750 



(5, 11) 



308-3 



12 



54 -500 



(0, 12) 



304-0 



13 



46 -875 



(0, 13) 



304-5 



14 



40 -375 



(10, 14) 



307-7 



15 



35 -125 



(10, 15) 



313-0 



Mean, . 



. . = 305-53"+ 07-1 (mean probal 



Die error). 



1 I counted tlie fourth obserration with double readings, equal in value to the 

 mean of the three obseiTations with siagle readinffs. 



