Robert Stevenson, Esq. 209 



whom is due tho honour of conceiving and executing the great work 

 of the Bell Rock Lighthouse, whose services were gratefully acknow- 

 ledged on his retirement from active duty, and will be long remem- 

 bered by the Board ; and to express their sympathy with his family 

 on the loss of one who was most estimable and exemplary in all the 

 relations of social and domestic life. The Board direct that a copy 

 of this resolution be transmitted to Mr Stevenson's family, and com- 

 municated to each Commissioner, to the different lightkeepers, and 

 the other officers of the Board.'' 



On the Connection between the Colour of Substances and their 

 Magnetic Properties. By RiGHARD Adie, Esq., Liverpool. 

 Communicated by the Author. 



The opinion that magnetism is a universal force, has of late years 

 rapidly gained ground, chiefly, I believe, through the discovery of 

 diamagnetism by Dr Faraday, which has called much attention to the 

 subject, both in this country and on the continent. It was while 

 examining a number of bodies on the torsion balance before a steel 

 magnet, that the idea of attempting to trace a connection between 

 the colours of bodies and their magnetism first struck me. The 

 experiments were being made with a view to endeavour to ascertain 

 by them the relation diamagnetism bore to magnetism, when the 

 evidence of the colour of a body being an index to some forces which 

 control its magnetism was so often repeated, that I determined to 

 examine this question, and it is the result of these enquiries I now 

 have to detail in the following pages. 



The torsion balance employed had a beam of three inches long, 

 suspended in a wooden case with a glass roof. The substances 

 examined were placed on either end of the beam, and their magnetism 

 there tested by approaching near to the point of rest of the balance, 

 a steel magnet weighing two ounces. Such an apparatus forms a 

 very delicate test for magnetism, in proof of which the operator, 

 after some experience, can repeat over and over again experiments 

 with bodies of the most feeble magnetic properties, and obtain by 

 them uniform results. The torsion balance takes cognisance of de- 

 grees of magnetism, long before a magnet will shew any attraction 

 when applied in the usual way ; but, with a body strongly attracted on 

 the torsion balance, there is another very palpable proof of magnetism. 

 The substance to be tested must be in a pulverized form, when it is 

 spread over a smooth sheet of paper ; if strongly magnetic on the 

 torsion balance, an ordinary steel magnet moved to and fro close 

 underneath the paper without touching it, will set some of the 



VOL. L. NO. C. — APRIL 1851. 



