72 W. Sturgeon, Esq., 07i the 



7. As brass in an alloy so extensively employed in the 

 construction of magnetic compass-boxes, its magnetic or non- 

 magnetic condition is an important scientific inquiry, which, 

 though for many years in the hands of philosophers, remains 

 at this day as undetermined as when first undertaken. That 

 certain pieces of brass have displayed unequivocal magnetic 

 action is a fact which cannot be questioned, but whether that 

 action was due to the alloy of pure copper and zinc alone, or 

 to portions of iron accidentally present in the metal, different 

 opinions have been entertained.* 



8. It has been supposed by Cavallo and other philosophers, 

 that all bodies, whether metallic or otherwise, are endowed 

 with magnetic powers, which vary considerably in degrees 

 of energy, whilst under the influence of, or operating on, the 

 magnetic needle. But when we meet with such conflicting 

 opinions as those that appear in the writings of philosophers 

 so eminent in this department of physics as Cavallo, Coulomb, 

 Bennet, Haiiy, Biot, Becquerel, and others who have entered 



suspended magnetic needle, one may easily discover in what part of it the iron 

 is lodged. 



*' 8th, In the course of my experiments on the magnetism of brass, I have 

 twice observed the following remarkable circumstance : — A piece of brass, which 

 had the property of becoming magnetic by hammering and of losing the magne- 

 tism by softening, having been left in the fire till it was partially melted, I found 

 upon trial that it had lost the property of becoming magnetic by hammering ; but 

 having been afterwards fairly fused in a crucible, it thereby acquired the pro- 

 perty it had originally, viz., that of becoming magnetic by hammering. 



" 9th, I have likewise often observed, that a long continuance of a fire so 

 strong as to be little short of melting hot, generally diminishes, and sometimes 

 quite destroys, the property of becoming magnetic in brass. At the same time 

 the texture of the metal is considerably altered, becoming what some workmen 

 call rotten. From this it appears, that the property of becoming magnetic in 

 brass by hammering is rather owing to some particular configuration of its 

 parts than to the admixture of any iron ; which is confirmed still further by 

 observing that Dutch plate brass (which is made, not by melting the copper, 

 but by keeping it in a strong degree of heat whilst surrounded by lapis calami- 

 navies) also possesses that property." 



* During the interesting series of experiments carried on by Professor P. 

 Barlow, on the magnetism of ferruginous bodies, the brass compass-box, and 

 several brass screws, belonging to one of the finest looking instruments em- 

 ployed, were found by that philosopher to be higly magnetic. — Barlow^a Mag* 

 n€f»c AxtrQ.<iti<>m, Second Edition, p. 17.) 



