Measures for Electric and Magnetic Quantities. 437 



directly observable quantities into the calculation, and to avoid 

 hypotheses. 



In § 622 Maxwell sets forth dimension-determinations for 

 the products and quotients of these twelve quantities, as given 

 immediately by their meaning. There are fifteen of these 

 determinations, in which those quantities referable to elec- 

 tricity are kept quite separate from those which refer to mag- 

 netism, so that (which is certainly remarkable) from these 

 fifteen determinations no relation between electricity and mag- 

 netism appears. I arrange them tabularly, retaining Max- 

 well's above-employed notation of the dimensions. 



No. 



Dimension. 



Electric quantities. 



Magnetic 

 quantities. 



1. 



L 2 M/T 2 



[,.E], [p.C] 



[m . 12] 



2. 



M/(LT 2 ) 



[©.<£], [C.B] 



[»•« 



3. 



T 



[e/G], O/E], [»/g] 





4. 



L 



[E/<£], [p/W] 



[G/0] 



5. 



L 2 



[>/£>], [0/g] 



[in/©] 



The last series of determinations result from the first, if they 

 be divided by the product of the quantities in question of the 

 second and fourth series. The fifth series may therefore be 

 omitted as superfluous ; then there remain the following iden- 

 tical equations between the quantities in the first four rows: — 



rj>i_ [p.Q] . r«q. 

 Lej|>.e] LcJ' 



[p-°]-[c] 

 [-E].[|] 



EI] 



Lastly, there are left three independent determinations for 

 the four magnetic quantities to, ft, 33, <£j, and seven for the 

 eight electric quantities e, E, p, C, Q, (f, (£, % If, therefore, 

 of these two groups one quantity each be defined by other de- 

 terminations — for example to and e, the quantum of magnetism 

 and the quantum of electricity — all the others are completely 

 defined, namely: — 



