1866.] 



Electricity given by Induction- Machines, 



177 



cell and a tangent rheometer of 950 spires, first the helix G, then that to 

 be determined, and lastly the sum of it and G. Assuming G= 1, we have 

 three equations to determine — the r of the helix in question, the remaining 

 r of the circuit, and the electromotive force of the cell. In deducing the 

 currents, the term involving sin-6 was used with a coefficient obtained by- 

 integrating through the length and breadth of the rheometer' s coil ; and 

 as its mean diameter is 6*4 times the length of its needle, and 6 never 

 passed 54°, I think the numbers of the Table are true to the last decimal. 



For brevity I symbolize the combinations, when in series, as a sum, 

 G+H ; when collateral, as a product G . H ; and for a reason which will 

 soon appear, when two are on the same primary I denote them hy a new 

 letter, as V=G+I. At first I used I and G on ; K and H on F\ To 

 prevent disruptive discharge, they were kept 1-5 inch asunder by disks of 

 baked wood. The results are given in 



Table II. 



Name. 







Spark. 



Sets. 



F" 



Sum of 

 components. 



n. 



b. 





X'OOOO 



1*0000 



in, 



3*95 



3-37 



1-23 

 2*49 





i-ooooo 





i-ooooo 



1*00779 



0-985385 



0-92306 



0*46542 

 0-44872 



H 



i-iooo 







I'OOOOO 



G+H 



G.H , 

 I 



1*0348 



1- 9988 



2*5343 



2- 7654 



1- 0096 + 



2- 0223 



4*3635 

 4*5358 



3 

 4 



1-02497 

 0-98837 



0-59167 

 0-60969 



2-0855 



2-00000 

 I -00000 

 0-23149 

 0-46298 



I+K 



G.H 1 



V+V , ,,, 

 V.Y' 



3 





3 •05 52 



6*5756 



0-80 



4 



0-46462 



4-6220 







0- 9996 



1- 9434 



1*3776 

 2*7319 



9*35 

 4*39 



3 

 I 



0-72562 

 0-71138 





2-46298 



0-83075 



F is computed with a correction for the place of the hehx on the pri- 

 mary, and with a resistance which includes that of the Weber =0-00779. 

 The Weber must have a considerable n of its own ; but as I did not know 

 its constants, and as this 11 must vary with the deflection, I did not com- 

 pute it. Possibly some of the discrepancies may be owing to this. The 

 sparks show the difference of tension ; they were taken with platinum 

 points, and when the machine was excited by four Groves. The column, 

 sum of components, gives for the collateral combinations the values which 

 arise from adding the <J> of each helix, taking into account the Weber's re- 

 sistance. 



1. It will be observed that G + H with twice as many spires, and V + V 

 with thrice as many as G, give the same current; so also that of I + K is 

 near that of I. 



2. On the other hand, G . H is twice G, and V . Y' twice V+V. 



3. It is also manifest that the effect of I is not proportional to its di- 

 minished resistance : its F is 4*4 times greater than that of G, but its actual 



These values of F should be multiplied by a factor representing the F of G, which 

 must be greater than its here assumed as unity. As, however, it belongs to all, its 

 omission does not ajffect the comparison. 



