120 Mr. W. Sturgeon on the 'niermo-Magnetism of 



demonstrative of the connexion in that class of homogeneous 

 bodies. And I am inclined to believe, that future labours in 

 this curious philosophical field of research, will ultimately 

 establish crystallography amongst those interesting sciences, 

 which are subordinate branches, and obedient to the laws, of 

 electricity. 



103. There are, however, thermo- magnetic phsenomena dis- 

 played by homogeneous metals, when experimented with in 

 certain forms, which do not appear to be very reconcilable to 

 the h3'pothesis of elcctro-a-ystallographij. They seem to de- 

 pend upon some other cause than any which that hypothesis 

 embraces : and as they are exhibited under different circum- 

 stances to any which have yet been noticed, the experiments 

 by which they are elicited will require to be described as a 

 distinct class. 



Seventh Class of Experiments. 



lot. Notwithstanding the opinions which have been set 

 forth to show that thermo-magnetic energies are not exalted 

 in combinations of metals, by employing them of large dimen- 

 sions, and that a pair of particles, however small, or wires 

 exceedingly thin, will develop the same extent of power as two 

 bars of considerable dimensions; I was led to imagine that 

 the same law might probably not extend to the innate mag- 

 netism displayed in homogeneous metals by heat. My in- 

 quiries were therefore directed to large masses of those metals, 

 in which, whilst experimented on in small pieces, I was unable 

 to discover the least trace of this extraordinary power; and 

 the results were such as to answer my anticipations in the most 

 ample and satisfactory manner. 



105. Experiments with large Masses of Zinc. — The first 

 piece of zinc in which I detected thermo-magnetic action was 

 a rectangular cake, or flag, which had neither been rolled nor 

 hammered. It was about 14 inches long, 8 inches broad, and 

 •75 inch thick, and weighed about 17 pounds. This mass 

 of zinc, when heated at one corner only, displayed magnetic 

 powers in a very exalted degree, and would deflect a compass 

 needle, on which the magnetism of the earth was not neutral- 

 ized, 20°, by the first impulse, when one of its edges was 

 held in the magnetic meridian and close to the glass cover of 

 the instrument ; but in consequence of a fracture in one of its 

 edges, the thermo-magnetic phasnomena were not so nicely 

 regulated in this piece as I have found them to be in other 

 masses of zinc, which are uniformly sound on every side. 

 I will therefore describe experiments which were made on a 

 whole sound flag of zinc, weighing 42 pounds, 2 feet long, 8*5 

 inches broad, and about 1 inch thick. 



106. The 



