114 DR. W. G. DUFFIELD, MESSRS. THOS. H. BURNHAM AND A. H. DAVIS ON 
Method 4 is a good one save for the effects of convexion currents which are 
considerable, because they rise over the curved side of the carbon. 
Table III.—Couples Due to a Single Arc. 
Current 
in 
amperes. 
a-h. 
a - c. 
a-d. 
a-e. 
- 9)- 
ai - h- 
fll - Cl. 
Mean. 
Total 
pressure 
in 
dynes. 
5 
o 
19 
o 
29 
o 
26 
t o 
21 
o 
26 
17 
o 
o 
e 
23 
0-32 
7 
40 
47 
27 
49 
50 
37 
48 
50 
43 
0-59 
9 
-- 
>54 
76 
71 
— 
— 
— 
— 
73 
• 
1-0 
Regarding the experiments upon alternating current arcs as a whole the results 
(Table I.) show a satisfactory measure of concordance for the various methods. 
i-o- 
0-5 - 
Alternating 
current 
o 
loAinps. 
Fig. 6. From Table I. 
Method 1 . . . O- Other methods ... #. 
Fig. 6 shows the results graphically, open circles representing the observations 
obtained by method 1, full circles the results of the other three methods. 
