118 Mr. W. Sturgeon on the Thermo- Magiietisni of 



regular masses, these experiments establish a very important 

 point, by exhibiting in the most striking and satisfactory man- 

 ner an intimate connexion between the crystalline arrange- 

 ment of the metal, and the distribution of the electric powers 

 by heat; for, to whatever point in the flat lamellated face of 

 this system or group of parallel scales heat was applied, the 

 electric forces were directed over the planes of the laminae 

 from the heated point ; and having traversed the general sur- 

 face of the metal, returned to that point again, across the edges 

 of the films, in precisely the same manner as in the experi- 

 ments with solid cones and cylindei's, — a circumstance highly 

 demonstrative that the thermo-magnetic forces in boih sets of 

 experiments have the same specific origin, and are actuated 

 by the same cause. The fountain of all the pha2nomena ap- 

 pears to be in the crystalline arrangement of the metal, and 

 the direction of the electric and magnetic forces to be refer- 

 able to the point of heat. 



96. It very often happens that fractures such as have been 

 described (88) (91), are bordered on some of their sides with 

 piles or groups of laminae, unfavourably situated for experi- 

 ments of this kind ; presenting their thin edges. Instead of 

 their planes, in the face of the fracture. When, however, the 

 method of experimenting becomes known, these trifling in- 

 conveniences are not of much consequence to the uniformity 

 of the thermo-magnetism displayed by the smooth part of the 

 fracture under examination. 



97. In the first place, the flat scaly surface on which the 

 experiments are to be made, ought to be as extensive as pos- 

 sible; at least two inches across; if larger, the better. Should 

 any side of this face present groups of the thin edges of la- 

 minae, they may be easily removed, either by the saw or by the 

 hammer: if those groups be not very extensive, their re- 

 moval will not be necessary. 



98. The principal circumstance next to be observed is, that 

 the flame of the spirit-lamp does not touch those unfavourable 

 crystals. The selected point of heat must always be on some 

 part of the flat lamellated face under examination, and near to 

 some angle. A momentary heat must suffice, and the plane 

 immediately and dexterously applied to the magnetic needle ; 

 the deflections of which will unerringly indicate the electric 

 current to be flowing over that surface_/?o;tt the heated point 

 to the opposite side. 



99. I have succeeded in discovering a method of forming 

 square bars or prisms of antimony, which observe a rigid 

 uniformity in the display of thermo-magnetic phaenomena, by 

 heating them either partially, or equably, ^at one end only. 



And 



