Lifting Power of the Electro-Magnet. 



511 



able, for at first I used too small a pressure, -which was not discovered till they 

 ■were reduced. They are 



Table XXI. 



The -weight hung to the lever = 14 lbs.; and the pressure P is (including 

 that due to the -weight of the lever itself) = 83-40. 



From tlie small value of z, the condition of the magnet is nearly that de- 

 scribed in (6), so that Mis the maximum, and M' the minimum force; and 

 they may represent the resultants of (0) -1- (12"8), and of (6"4) -f (6*4). In 

 the ordinary arrangement with a spiral on each arm, each of them would excite 

 M at its own arm, and M' at the other ; the Z, therefore, corresponding to 

 2f = 249-38 is the resultant of 2i)!f + 2il/'. By interpolation and Table viii. 

 it appears that this = 746-91, only 0-763 of 982-15, the sum of the compo- 

 nents. 



A more complete series was made with the helices F, F'. The results are 

 reduced to 549-08, W= 24, and P= 141-20. 



Table XXll. 



3x2 



