0 —h, hy — dx 
we | hs 0 Each, cy dy 
Winn = 
—hy hy 0 En d, 
dy dy d, Q 
(B) is brought into the form A = —g (d + {v hl) 
da od ; 
(C’}) becomes curl h = 9 — + — 
de OF 
div d= eo 
D ld dh 
(1) curl d= — 
div h=0O 
(i) gives as tension components the tensions of MAXWELL, as energy 
current Poyrrinc’s Vector and also the right density of energy. 
If the three-dimensional vector, the components of which are q,, 
q, and q, is denoted by A and if we put 
=P 
then equation (A) may be written in the form 
h == curl A 
1 l De 
QO == | 2/0 ¢ — — 
: / OL 
Using the notation of Laur*) and writing Wp” —— M,,, we obtain 
the equations 
Do tg ai ee ee Bei 
Di Mr ote ae ne eee ee EN 
Lesl (MoMA | ce ete neh Seer 
Ks Dig Tie Verne eN 
M = Retq. 1 ee eee 
Physics. — “Hlectric current measuring instruments with parabolic 
law of deflection”. By Prof. J. K. A. WERTHEIM SALOMONSOK. 
(Communicated in the meeting of November 25, 1916). 
In current or voltage measuring instruments the deflection is 
either about proportional to the current strength passing through 
the instrument or it grows with the square of the current strength. 
In this way they constitute two different classes of instruments. 
The ordinary galvanometer with a movable coil or magnet belongs 
1) M. Lauw. Das Relativitätsprinzip. 
