Lifting Power of the Electro-Magnet. 515 



a = 0-001094+ Jxlog-' (6-17319)+jxlog-' (4-90309). 



^ = 00000989 + -J X log-' (4-34242) + f x log"' (3-25527). 



7 = 0-00000002733 + ^ x log-' (2-14768). 



The case is, however, very different if those parts of the circuit, which are 

 not directly excited, be lengthened. With the cylinders = 10-1, and the lielices 

 (B), two inches high, placed in contact with the keeper, I got with ^=544-83: 



Table VII. 



(15) 



Tliese give 



L = 810-84 \\-t. log-' (6-99120) + t- . log-' (4-62797 ) 



-<Mog-' (2-21015) I, 



when the coefficients are less than even in (12), but the law is the same as 

 in the rest. The places of the minimum and maximum are much higher, and 

 the change of i is greater than in any of the others. 



The terms within the brackets in these expressions are, I tliink, indepen- 

 dent of ^ ; for in my former paper it is shown that, with the magnet there used, 

 the decrease of Z for a given difference of t is the same, with very considerable 

 variations of the current. 



ACTION OF SPIRALS. 



I. In the first instance, I give the Table already referred to of the spirals 

 {^A ), which I assume as my standard. Their constants are 



6z=l-14; 6' = 2 80; 5 = 40. 

 Their external diameter was intended to be as large as the distance of tlie 

 cylinders would admit, and the cylinders themselves are shortened to 0-15, 



VOL XXII. 3 X 



