226 



The Astronomer Royal's Experiments on 



magnet, or for the case of a galvanic coil enclosing an iron core; 

 but it will not apply to the case of a galvanic coil without an 

 iron core : for that case the axis of the small magnet in the 

 positions numbered 35, 5, 12, 46, and all to the right of it 





must be directed almost exactly to the centre of the right-hand 

 end of the magnet, and a similar direction must be made at 

 65, 27, 20, 54 in respect of the left end, with corresponding 

 changes for intermediate stations. 



The angles of position were never measured; but they are 

 fully taken into account in the subsequent resolution of forces 

 into longitudinal and transversal components. 



The following Table (p. 227) exhibits the total force at each 

 station, as ascertained by the operations described above. It 

 will be remembered that the numbers for the " Galvanic coil with 

 iron core " are not necessarily on the same scale as those for the 

 " Large magnet, ;; and that the numbers for the " Galvanic coil 

 without core" must be divided by 120 to make them com- 

 parable with those for the " Galvanic coil with iron core." 



Perhaps the following points are worthy of present notice : — 



1. Remarking that, in the experiment in which the edge of 

 the large magnet is presented to the small magnet, the distance 

 of the small magnet is in each circuit the same at every station, 

 it will be seen that the greatest directive force is not longitudinal 

 at the end of the magnet, but transversal, at about -^ part (or 

 probably less) of the length from the end of the magnet. 

 There is, however, a diminution and then an increase in 

 proceeding from either of these positions to the other ; and the 

 directive force opposite the middle of the magnet's length is less 

 than either of them ; so that, in making the entire circuit of the 

 magnet, there are six maxima and six minima. 



