M. A. Berlin on Circular Magnetic Polarization, 



4-91 



2. Rotations jfroduced hy some aqueous solutions. 

 Name of liquid. Concentration. Thickness. Rotations. 



Chloride of calcium . 

 Chloride of calcium . 

 Chloride of calcium . 

 Chloride of calcium . 



Water 



Chloride of magnesium 

 Chloride of magnesium 

 Chloride of magnesium 



"Water 



Chloride of zinc . . 



Water 



Chloride of strontium 



Water 



Nitrate of ammonia . 



Water 



Sulphate of iron . . 

 Water . . . • . 



Chloride of magnesium . ... 



Chloride of strontium 



Alcohol of 36° Beaume . ... 



Distilled water 



The rotatory power of sulphuret of carbon is remarkable ; 

 it is three times greater than that of water, and only twice less 

 than that of the flint-glass of Faraday. This liquid is conse- 

 quently valuable, because it may be substituted for the majo- 

 rity of the rare glasses required for this class of experiments. 

 In the same substance the rotation varies in intensity with the 

 thickness ; but the law which regulates this variation has been 

 differently expressed by the various experimenters who have 

 studied this subject. Some have stated that the rotation was 

 proportional to the thickness ; others that it was independent 

 of it; and others, again, that it increased with the thickness 

 up to a certain limit, from which it diminished, and was finally 

 reduced to zero. It is easily seen how much is true and how 

 much is erroneous in these assertions. 



In the first place, it is evident that if we consider the action 

 of a single pole on a substance of indefinite length, this action, 

 variable with the distance, will decrease from the first layer 

 to the second, from the second to the third, to a certain di- 

 stance, beyond which it will be null; so that the more distant 

 layers will no longer be acted upon by the magnetism. The 

 effects upon all the successive layers being added together, it 



