1 08 Mr. W. Spottiswoode on the Geometrical 



2700. There can be no doubt that the copper linings, when 

 in place, were full of currents at the time of action, and that 

 when away no such currents would exist in the air or glass 

 replacing them. There is also full reason to admit, that the 

 divergence and convergence of the magnetic lines of force 

 supposed above (2697.) would satisfactorily account for such 

 currents in them, supposing the indirect action of the cores 

 were assumed. If that supposition be rejected, then it seems 

 to me that the whole of the bodies present, the magnet, the 

 helix, the core, the copper lining, or the air or glass which 

 replaces it, must all be in a state of tension, each part acting 

 on every other part, being in what I have occasionally else- 

 where imagined as the electro-tonic state (1729.). 



2701. The advance of the copper makes the lines of mag- 

 netic force diverge, or, so to say, drives them before it (2697.). 

 No doubt there is reaction upon the advancing copper, and 

 the production of currents in it in such a direction as makes 

 them competent, if continued, to continue the divergence. But 

 it does not seem logical to say, that the currents which the- 

 lines of force cause in the copper, are the cause of the diver- 

 gence of the lines of force. It seems to me, rather, that the 

 lines of force are, so to say, diverged, or bent outward by the 

 advancing copper (or by a connected wire moving across lines 

 of force in any other form of the experiments), and that the 

 reaction of the lines of force upon the forces in the particles 

 of the copper causes them to be resolved into a current, by 

 which the resistance is discharged and removed, and the line 

 of force returns to its place. I attach no other meaning to 

 the words line of force than that I have given on a former 

 occasion (2149.). 



Royal Institution, Dec. 14, 1849. 



X. On the Geometrical Interpretation of Quaternions, 

 #j/Willi am Spottiswoode, M./L, of Balliol College, Oxford*. 



§ 1. Fundamental Laws. 



THE following investigations refer to the same subject as 

 that treated by Professor Donkin in vol. xxxvi. of this 

 Journal; and are offered, not as at all preferable to his, but 

 simply as indicating another mode in which the question maybe 

 viewed; it being desirable to exhibit a subject, which is some- 

 what new, in more than one way, in order that as much light 

 as possible may be thrown upon it. The present paper will be 

 interesting (if it is so at all) principally because its results are 

 substantially the same as those of the paper just referred to, 

 * Communicated by the Author. 



