and Phenomena of Magnetic Induction. 265 



sisted by its repulsive action, the westerly deviation of the north 

 end of the needle. 



Successive trials were then made on the unaided action of the 

 magnets on the compass at the respective distances, as well as of 

 the increase produced by the mean action of the different ends 

 of the iron-bar. The results are here exhibited. 



Now, the comparative forces, as represented by the difference 

 of tangents, of the magnetism induced into the iron-bar, under 

 the two conditions of direct induction on the nearest end, and 

 of developed induction on the end most remote from the mag- 

 nets, were as follows : — 



• The great difference of the results of the first length betwixt the two 

 series of experiments on the direct induction on the nearest end of the bar, 

 requires explanation. It may arise from two causes, the difficulty of placing 

 the magnets when there were four in number, to act equally and tangentially 

 as one magnet, when the distance between the tray of magnets and the com- 

 pass was so small, and the importance of the smallest error of observation 

 when the tangents of deviation are so great. The first cause, however, 

 being considered as the principal one, the first experiment of the second 

 series was made in a different manner, by arranging the magnets in a verti- 

 cal parallel series, so as to concentrate their action more strictly into the 



