70 Royal Society : — Rev. T. B, Robinson on increasing 



cores might not influence the results, and tried this with P', P'", and 

 one P v , whose core =1*90 inch in diameter and 15-5 inches long. It 

 has 349 spires of No. 15 in two layers. G was put on each of them, 

 and currents transmitted, which made their M^s nearly equal. 



Table III. 



Name. 



Sect, of 

 core as 



$. 



Sets. 



Spark. 



**". 



P" 



I •GO 



2-04 



3'o° 



1-0414* 



I'OOOO 



1*0054 



3-5 



2* 



2* 



2*225 



3' 2 37 

 2-662 



1169 

 1168 

 1156 



piv 



Pv 





It follows from this that the least of these cores is large enough 

 for the excitation produced by four cells : the size does seem to in- 

 crease the spark, though this increase may be owing to better insula- 

 tion of the core-wires in P'" and P v f. 



The following results were obtained with the mechanical rheotome 

 worked at a uniform speed of 13 discharges per second. 



Table IV. 





#. 



F. 



Sets. 



F* 



Sum of 

 components. 



n. 



b. 



a 



I'OOOO 



1-8832 

 1-3149 



3*0402 

 1-4196 



1-9882 



2'5535 

 2*5580 

 2-6465 

 3-5558 



4 - 3*79 

 5-1460 

 6-0758 

 2-5207 

 1-7616 

 1-6687 

 3-4596 

 8-1939 



1 -oooo 

 4-5106 



1-6143 

 5-3109 

 1-3578 



2'OI 12 

 5'4IOO 

 4-3 6 35 

 4-3 6 35 

 5-2464 



6-5756 

 6-9400 



8-2081 

 5-4586 

 5-4586 

 4-9644 



9-5774 

 I 5'739§ 



19 

 2 



11 

 2 

 2 

 1 

 2 



5 



1 



3 

 3 

 3 

 2 



4 

 1 



I'OOOOO 



0-41752 



0-81451 



0-57159 

 1-0455 1 

 0-99855 



0-47202 

 0-58623 

 0-60651 

 0-67776 

 0*65666 



0*74153 



0*74030 

 0*46179 

 0*32271 

 0*33614 

 0*36124 

 0*52058 



2*8324 



r 3-8594 

 4*1799 

 4-6932 

 6*0488 



3-4996 

 8*2736 



I'OOOOO 



o*6+ 

 i*6 + 



I'OOOOO 



0-56286+ 



0-31646 

 0*23149 

 0-23149 



0-63292 

 0-73130 

 0-65810 



1-00779 

 0-34624— 

 075002 — 



0-85385 



0*92704 



0*27756 



0-46542 

 0*46542 



C'26862 



0*23248 

 0*28543 



L=I+K ... 



Gr+L 



O.L 



H 



C=A+B ... 



N 



I 



K 



G-.K 



G.L.H 



a.L.o 



G.L.C.H... 



M+N 



-0 



S = M+N ... 

 L.O 



MNIK ... 



1 . As before, two helices in series give no increase of quantity ; 

 M + N is the same as N, G + L nearly the mean of G and L. 



2. The quantity of collateral helices is seen in column 6 (as in Table 

 II.) to be the sum of the separate actions of each. The discrepan- 

 cies are not greater than what can be explained by the uncertainties 

 inherent in these measures, which I have already described. One 



* 2-5 sets taken on the first day were very unsteady. The one taken on the 

 second was close, and gave 1 0207. 



f At the same time I tried two helices similar to A and B, except that their 

 wire is varnished iron, which were given to me by Dr. Callan. Their * is 

 06887, and their spark only 0524 in. The $ of A + B is 29138 times as 

 great, a difference caused solely by the greater resistance of the iron. 



