5f0 PLUCKER ON THE ACTIOX OF THE MAGNET 



remaining rectilinear in the centre, formed a curve with its con- 

 cavity turned towards the watch-glass. 



38. The two halves of the keeper were next placed at a distance 

 of 23 miUims. ; the fluid then projected even beyond their upper 

 angles. On closing the circuit the fluid became extended into 

 an elongated oval, the gi-eatest dimension of which coincided 

 with the ax'lal direction. In the centre, the surface of the fluid 

 was depressed almost to the glass, and became accumulated 

 perpendicularly above the angles of the two halves of the keeper. 

 The view from above is represented in fig. 1 1 ; the section in 

 the direction of A B in PL IV. fig. 11 c. In the equatorial 

 plane the oval was somewhat compressed in the centre; the sec- 

 tion in this plane corresponded with the upper surface of the 

 watch-glass. 



39. Lastly, the poles were placed at a distance of 31 millims." 

 apart, so that the original circle formed by the liquid was en- 

 tirely contained between the halves of the keeper. On exciting 

 the magnetism, it was converted into a slightly excentric ellipse, 

 the long axis of which was in the meridional plane (PI. IV. 

 fig. 12). In the equatorial plane the surface of the liquid was 

 slightly depressed. 



If, with the gi'eatly diminished magnetic tension consequent 

 upon the separation of the halves of the keeper, a current of 

 greater intensity had been used and the liquid had reached the 

 halves of the keeper, it would of course have assumed a form 

 somewhat approaching that seen in the preceding case. The 

 gradual transition of the form in fig. 8 to that of 12 may be 

 readily followed, and considered as necessarily dependent upon 

 the attractive forces and the cohesion of the liquid. 



40. Proiochloride of iron, when dissolved in water, was found 

 to be somewhat less strongly magnetic than the perchloride, and 

 protosulphate of iron still less so. When the arrangement was 

 the same as in paragraph 34, a concentrated solution of the 

 latter in the watch-glass formed a circle 26 millims. in diame- 

 ter, which on the excitation of the magnetism was converted 

 into an ellipse-, the axes of which were 27*5 millims. and 23*5 

 millims. in length. 



41. A saturated solution of pernitrate of nickel was more 

 powerfully magnetic than the solution of the protosulphate of 

 iron : at first it formed a circle 30*5 millims. in diameter, and 



