216 Richard Adie, Esq., on the Connection between the 



magnetic metals, iron, nickel, and cobalt, to throw down a much 

 larger proportion of coloured substances than the diamagnetic 

 metals. 



It is on these results that I rely for proof of the connection be- 

 tween the colour and the magnetic properties of bodies; their general 

 tendency is to shew that, when the forces of aggregation which 

 bind the particles of a substance together produce transparency or 

 whiteness, such a combination has feeble magnetic properties ; and 

 when the same forces produce a dark or dull coloured substance, 

 then the magnetic power is more developed. For the proof of 

 this I have given the comparison among a number of bodies of like 

 constitution, where the rule has appeared invariable ; but if a simi- 

 larity of constitution be disregarded, exceptions can be readily given ; 

 if transparent iron alum, sulphate of manganese, or nitrate of silver, 

 be compared with dark-coloured sulphurets of potassium or sodium, 

 there is then no connection to be traced between colour and mag- 

 netic properties. The relation, then, between colour and magnetic 

 attractions of bodies must be held to rest only among those of simi- 

 lar constitution. 



In the course of the experiments I have given, the tendency of 

 oxygen, where it forms a dark-coloured oxide, to develope decided 

 magnetic attraction, has been shewn in the case of copper and silver ; 

 where oxygen unites to form colourless combinations, the great 

 majority of these are either diamagnetic or are feebly attracted. Dr 

 Faraday has shewn that water and the gaseous transparent oxides are 

 repelled by the magnet. In my experiments with the torsion balance, 

 rock crystal, Iceland spar, boracic acid, sugar, starch, resins, all of 

 them colourless bodies containing oxygen, are repelled by the magnet ; 

 while talc and alum or sulphate of potassa and alumina, are feebly 

 attracted. — Atmospheric air drawn by a fine-pointed pipet from 

 between two highly-magnetised steel surfaces, when tested for oxygen, 

 gave the usual proportion. Now, when bodies are decidedly magnetic 

 in themselves, this distinguishing feature can be traced in the greater 

 part of their combinations. This is the case for the four magnetic 

 metals, iron, cobalt, nickel, and manganese, where the ferrocyanide 

 of potassium is the only exception. In the oxides, the diamagnetic 

 transparent ones are so numerous that it appears to me fair to argue 

 from them that oxygen, like p\ire diamond, has only feeble magnetic 

 properties. The attraction of talc and alum I do not consider to 

 militate against this view, for the aluminum contained in them has 

 very decided magnetic properties. 



From inorganic matter I turned to examine some organic bodies 

 where colours of the most surpassing beauty are prepared in nature. 

 The wings of British moths and butterflies were tried on the torsion 

 balance ; but these, beginning with the white cabbage butterfly, 

 being all attracted, gave me no evidence. One specimen, the body 



