Homogeneous Bodies ; "mth illtistra live Experiments. 119 



And I now find that I can predict with certainty the mag- 

 netic character of any side of the bar, by paying attention to 

 certain circumstances connected with its casting. I have cast 

 several sets of square bars, of an uniform size and figure, under 

 precisely the same circumstances, and have never yet found 

 one single bar to deviate from the general law. One of those 

 sets consisted of fifteen bars, all of which observed the same 

 laws of thermo-magnetic action. 1 have, however, in vam tried 

 to obtain them of an uniform power, the thermo-magnetism 

 of some of them being much more energetic than that of others. 

 This circumstance, which I hope soon to obviate, and some 

 others which I find associated with the display of their thermo- 

 magnetic phsenomena, but which I have not yet had time to 

 investigate, prevents my giving a description, in this place, of 

 the circumstances under which I have hitherto cast these prisms 

 of antimony; the thermo-magnetic character of which can 

 easily be predicted before the metal enters the mould*. 



100. In general, these bars possess a considerable degree 

 of power as thermo-magnets; and when four, or more of them 

 are properly combined, their conspiring energies on the mag- 

 netic needle may be very satisfactorily exhibited to every 

 auditor in the most spacious lecture-room. 



101. I have also been enabled to cast discs of antimony, 

 which do not vary from each other in the character of their 

 thermo-magnetic qualities. I have not however, as yet, had time 

 to investigate the whole of the circumstances which I suspect 

 to be connected with the communication of that power to the 

 metal, and therefore beg permission to reserve the detail of 

 the experiments till another opportunity. I mention them 

 in this place merely as facts, which 1 can at any time repeat. 

 I will further observe, however, that I am of opinion that the 

 thermo-magnetism displayed in the prisms and discs already 

 noticed, may be traced to the same source as that displayed 

 in other forms of antimony; that is, to the crystalline arrange- 

 ment of the metal ; and that electricity is intimately associated 

 with the process of crystallization generally. This opinion 

 is highly favoured by the well-known fact of electro-polarity 

 being exhibited in the tourmaline and some of the crystallized 

 gems : and as regards the metals, I imagine that the experi- 

 ments and observations I have hitherto detailed, are amply 



* It is next to impossible to cast bars of antimony of considerable di- 

 mensions which will not exhibit magnetic phanoniena by heat; indeed, 

 bars of almost any size, or masses of any figure whatever, whether regular 

 or irregular, display those powers more or less. It however re<|uircs con- 

 siderable attention to obtain several [ueccs of antimony which will observe 

 an uniformity of thermo-magnetic action. 



demonstrative 



