in Magnetism and Electricity. 



89 



length (23), and its resistance was about four-tenths of that of 

 the wire surrounding the armature. The experiments were con- 

 ducted in the same order as those in the preceding series, the 

 thin cardboard being still interposed between the submagnet 

 and the electromagnet (24) ; and the following Table contains 

 the results obtained. 



Table III. 



Number of magnets 

 on cylinder. 



Weight, in ounces, 



required to separate 



submagnet from 



electromagnet. 



Squares of magnetic 

 force of magnet- 

 cylinder. 



1 

 2 

 3 

 4 



5-00 



28-00 



76-00 



144-00 



5 



20 

 45 



80 



i 



29. From a comparison of the numbers in this Table with 

 those in Table II.., it will be seen that the ratio of increase, as 

 well as the amount of the magnetism induced in the electro- 

 magnet, has been considerably augmented by an increase in the 

 length of the electromagnetic circuit. 



30. Experiments were also made with the submagnet in direct 

 contact with the electro-magnet without the interposition of the 

 cardboard, the arrangement of the electrohelices remaining the 

 same as in the preceding experiments (28) . The small scale- 

 beam and stand were removed from the lathe-bed, and were 

 replaced by a stronger apparatus of a similar construction. The 

 results of these experiments are shown in the following Table. 



Table IV. 



Number of magnets 

 on cylinder. 



Weight, in pounds, 



required to separate 



submagnet from 



electromagnet. 



Squares of magnetic 

 force of magnet- 

 cylinder. 



1 

 2 

 3 

 4 



31-50 



98-00 



150-50 



178-50 



31-50 

 126-00 

 283-50 

 504-00 



31. From an examination of the results of these experiments, 

 it will be seen that when the submagnet was in direct contact 

 with the electromagnet, the force required to separate them was 

 very greatly increased; but the ratio of this increase, as mea- 

 sured by the same means as in the former experiments (22), is 

 very considerably diminished ; for when one magnet was placed 



