2 Mr. W. Sturgeon on the Thermo- Magtietism of 



mode by which he calls forth the electric powers, and interro- 

 gates the magnetic phaenomena they display. 



4. In this mode of research, however, as well as in the 

 former, combinations of two, or more distinct metallic bodies 

 were still employed ; and it appears that, by whatever inge- 

 nious contrivances other philosophers have pursued the in- 

 quiry, combinations of two, or more bodies have generally been 

 considered necessary for the display of thermo-magnetic phas- 

 nomena. I am not aware, however, that any experiments are 

 yet before the public illustrative of thermo-magnetic action 

 in one solitary piece of metal, or other homogeneous body. 



5. In my " Recent Experimental Researches in Galvanism, 

 Electro- Magnetism, &c." a small work lately published, I 

 have stated that simple metallic bodies not only display dif- 

 ferent electric powers as regards each other, but also that 

 the various parts of each separate metal are relatively in dif- 

 ferent electric states at one and the same time, although in 

 close connection with each other by the best known conduct- 

 ing material ; that is, by the metal itself. And I have shown 

 by several experiments on homogeneous metals, that those 

 magnetic powers, which are regarded as inseparable from the 

 electric, can readily be brought into play either by the gal- 

 vanic or by the thermo pi'ocess, — a circumstance, which to 

 me appeared highly confirmatory of the hypothesis. 



6. Since writing that work, I have been induced to prose- 

 cute those inquiries to a still greater extent ; and the experi- 

 ments and observations which are now about to be described, 

 appear to me to permit no further question as to the existence 

 of thermo-magnetic powers in most, if not in all, of the homoge- 

 neous metals; individually, and independently of any con- 

 nection with each other. And the phaenomena they display, 

 are, in many cases, as decidedly obedient to certain unerring 

 laws, as in any thermo-magnetic aiTangement whatever. 



7. My first experiments for the detection of magnetism 

 by heat in single pieces of metal were not very successful ; 

 although the pieces were alloys, and consequently not homo- 

 geneous metals. I found however, after some trials, that by 

 hardening one end of a piece of steel, and keeping the other 

 end quite soft, the thermo-magnetic energies were always 

 called into play when any part near to the centre of the bar 

 was heated, and the extremities left at the ordinary tempera- 

 ture of the atmosphere. 



8. Brass also, by the same treatment, displays thermo- 

 magnetic properties, which are easily detected by the galvano- 

 meter. It is a remarkable fact, however, that the electric cur- 

 rent in these metals proceeds in opposite directions as regards 



the 



