to Magnecrystallic Action. 



137 



s 



that researches in magnecrystallic action have established, namely, 

 that the self- same arrangement of particles influences the pai'a- 

 magnetic and diamagnetic forces in the self-same way, intensifying 

 both in the same direction. Let us suppose, then, that the 

 sphere of carbonate Pig. 3. 



of iron is suspended 



as in fig. 2, the line 

 ab being the axis of 

 the crystal. I have 

 already shown that 

 this line is that in 

 which the magnetic 

 induction is most in- 

 tense*. Comparing, 

 as before, the lines ab and cd, the friendly pole a is stronger than 

 c, and the hostile pole b is stronger than d; a residual " couple " 

 therefore acts upon ab in the direction indicated by the arrows, 

 which will finally set this line parallel to the direction of the 

 force. This is also the result which experiment exhibits. 



We will now proceed to apply the principle of polarity to some 

 of the more complicated forms of magnecrystallic action. Some 

 highly paradoxical efi'ects were adduced by Mr. Faraday as illus- 

 trative of his earlier impressions regarding this question, and I 

 cannot bring the subject in a clearer manner before the reader 

 than by quoting Mr. Faraday's own description of the phseno- 

 mena referred to. Here it follows : — 



" Another very striking series of proofs that the efi'ect is not 

 due to attraction or repulsion was obtained in the following 

 manner. A skein of fifteen filaments of cocoon silk, about 14 

 inches long, was made fast above, and then a weight of an ounce 

 or more hung to the lower end ; the middle of this skein was 

 about the middle of the magnetic field of the electro-magnet, and 

 the square weight below rested against the side of a block of 

 wood so as to give a steady silken vertical axis without smng or 

 revolution. A small strip of card, about half an inch long and 

 the tenth of an inch broad, was fastened across the middle of this 

 axis by cement ; and then a small prismatic crystal of sulphate 

 of iron 0"3 of an inch long and 0* 1 in thickness, was attached 

 to the card, so that the length and also the magnecrystallic axis 

 were in the horizontal plane ; all the length was on one side of 

 the silken axes, so that as the ci-ystal swung round, the length 

 was radius to the circle described, and the magnecrystallic axis 

 parallel to the tangent. 



" When the crystal was made to stand between the flat-faced 

 poles, the moment the magnet was excited it moved, tending to 

 ♦ Phil. Mag. S. 1. vol. ii. p. 177. 



