the Electricity given by Induction-Machines. 



GO 



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 by a new letter, as V=G + I. At first I used I and G on P f " ; 

 K and H on P iv . To prevent disruptive discharge, they were kept 

 1*5 inch asunder by disks of baked wood. The results are given in 



Table II. 



Name. 



g 



H...... 



G+H. 

 G-.H . 



I 



I+K ., 

 G.H 

 (I+K) 

 V+V\. 

 V.V .. 



$. 



•0348 



2'5343 

 27654 



3-°552 

 0-9996 

 1-9434 



F.* 



Spark. 



Sets. 



4> 

 F* 





in. 







I'OOCO 



3'95 





roocoo 



I'lOOO 



1-0096 + 

 2-0223 

 4'3 6 35 

 + 5358 



3'37 



1-23 



2-49 



3 



4 



3 



1-02497 

 0-98837 

 0-59167 

 0-60969 



6'5756 



o-8o 



4 



0-46462 



1-3776 

 2-7319 



9'35 



4*39 



3 

 1 



0-72562 

 0-71138 



Sum of 

 components. 



2-0855 

 4-6220 



JI. 



I'OOOOO 

 I'OOCOO 

 2'OOCCO 

 I'OCOCO 



0-23149 



0-46298 



2-46298 



1-00779 



o'9 8 5385 

 0-92306 



0-46542 

 0*44872 



0-83075 



F is computed with a correction for the place of the helix on the 

 primary, and with a resistance which includes that of the Weber 

 = 0*00779. The Weber must have a considerable II of its own ; but 

 as I did not know its constants, and as this n must vary with the 

 deflection, I did not compute 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 <i> 

 of each helix, taking into account the Weber's resistance. 



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 . V twice V + V. 



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

 its diminished resistance : its F is 4*4 times greater than that of G, 

 but its actual current is only 2 5. This is at once explained by its b 

 being so much less. So also the ratio of the theoretic to the effec- 

 tive current is nearly unity in G + H, while it is only 0*73 in V + V, 

 and for the same reason. In G . H . (I + K) the ratio is still smaller ; 

 but I shall recur to this. 



I now used the four primaries I + K=L on P 1V , single helices 

 on the others. I had some doubt whether the difference of the 



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

 which must be greater than its «i>, here assumed as unity. As, however, it belongs 

 to all, its omission does not affect the comparison. 



