Lifting Power of the Electro-Magnet. 



509 



Table XX. 



In each of these the relation between the resultant and components is dif- 

 ferent ; for instance, i (1000) is composed of 2L (500) ; no-w its ratios to one 

 of them are — 



1-2410; 1-2396; 1-1384; 1-4364. 



Again, taking L (600) as composed of 2i (300), they are — 



1-3050; 1-3818; 1-2143; 1-6139. 



It will also be observed that when the components are unequal, the smaller 

 one adds but little to the resultant: thus (100) adds but 22-56 to (900); (200) 

 adds 51-18 to (800), in the first magnet, — not a tenth of -what they -would 

 produce alone. If the ratio of the L in the second column to the others which 

 have the same ^ be taken, it is found to vary but little in the hollow and small 

 ^!^^et, except in if- =100, where the excitation seems scarcely sufficient to 

 bring the iron into full action ; in the first it decreases, in the other increases, 

 as ^ diminishes. For the large magnet it decreases more rapidly, being 1-2611 

 for ^- 1000, 0-9113 for ^ - 300. Probably in all these the central portion of 

 the magnet has not been excited. 



3. I thought the complexity of this investigation might be diminished by 

 using a single spiral or helix, and thus having only to deal with the inductions 

 {z) and {c — z). In the ordinary course of my experiments, with each arm 

 equally excited, the force at each polar surface is equal, and as the keeper is 



VOL. XXIII. 3 X 



