68 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
Two spherical surfaces, 0'75 inch radius, diameters 0’4 and 0‘55 inch respectively. 
Date. 
No. of cells. 
Striking distance. 
Curve. 
inch. 
Feb. 12, 1876 
600 
0-00120 ") 
1200 
0-00350 1 
YI. 
1800 
0-00930 f 
2400 
0-01400 J 
Jan. 13, 1876 
1080 
0-00425 1 
2160 
0-01325 | 
3240 
0-02200 !>• 
VII. 
4320 
0-03500 
5400 
0-04600 J 
These numbers were plotted down on paper ruled in millimeters, the abscissae 
representing the number of cells (50 millimeters to 1000 cells) and the ordinates 
the striking distance (40 millimeters to ‘01 inch). With the curves drawn to this 
scale, it was practicable to estimate to the tqoWo of an inch. 
The following striking distances were obtained by reading off the ordinates at the 
various numbers of cells given in Table I. : — 
Table I. 
From 
No. of cells. 
curve 
250 
500 
1000 
1500 
1 
2000 
2500 
3000 
4000 
1 
5000 
6000 
7000 
80C 0 
L 
0 '00125 
0-00252 
0 -00525 1 
0 00920 
0-01312 
0 -01775 
0 02275 
003325 
0 -04433 
_ 


n. 
0-00125 
0-00248 
0 -00480 
0-00850 
001325 
0 -01800 
0 -02330 
0-03468 
004625 
0-05833 
0-07025 
0 -08250 
in. 
0-00125 
0-00250 
0 -00480 
0 -00875 
0-01375 
0-01900 
0-02380 
0 03460 
0 -04575 
005750 
0-07075 
0-08250 
IV. 
o-ooioo 
0 00200 
0-00400 
0 -00825 
0 -01275 
0 -01775 
0 -02230 
0-03400 
0 -04500 
0-05678 
0-06900 
0-08150 
V. 
0 -00125 
0 -00250 
0-00512 
0-00850 
0-01275 
0 -01700 
0 -02250 
0 -03360 
0-04485 
0 -05525 
0 -06700 
0-07950 
VII. 
o-ooioo 
0 00200 
0 -00385 
0 -00775 
0 -01118 
0 01600 
0-02000 
0-03100 
0 -04175 
— 
— 
Means 
0 00117 
0 -00233 
0 00464 
0 00849 
0-01280 
0-01758 
0 -02244 
0 -03352 
0 -04465 
ii -05696 
0 -06925 
0-08150 
VIII. 
0 -00125 
0 -00225 
! 
0 -00500 
0-00846 
0-01275 
0 -01752 
0 02300 
0-03350 
0 -04512 
0 -05700 
0 06930 
0-08180 
We were led to adopt the numbers given at VIII. as more nearly representing a 
true mean curve, the judgment being guided by an inspection of the several curves 
representing the individual observations (Plate 6). 
Curve VIII., it will be seen, runs very smoothly and tends to show that up to p, 
difference of potential of 8000 cells there is not any common factor which can be 
used as a multiplier to furnish the striking distance for a given number of cells ; for 
the differences between the striking distances of consecutive equal numbers of cells is 
an increasing quantity, the increment of increase is, however, very small after 
4000 cells have been reached. 
Prom the mean curve VIII. the following ratios for a given number of cells were 
obtained : — 
