Chemistry and Physics. 229 
The double image prism doubling both rays makes the ordinary 
ray from one source coincide with the extraordinary ray from the 
other. But in general each of the elementary rays emerging from 
the plate of quartz is polarized elliptically, and we know that this 
kind of light after having traversed any doubly-refracting analy- 
zer gives two images of unequal intensity polarized at right-angles, 
but whose sum is constant and equal to the sum of the squares of 
the velocities parallel to the two axes of the ellipse. The beam, 
n 
completely unpolarized, if the two parts are equally illuminated. 
Above and below will be spectra traversed with bands, the dark 
— Comptes Rendus, \xxviii, 1497. oo) le OE. 
The Selection and Nomenclature of Dynamical and Elec- 
and time, which he has chosen as the basis of his system. ‘T 
hecessity will be obviated, if one definite selection of three funda- 
ctors, must ‘ 
of fundamental units of force, work, electrostatic, and electro-_ 
e carrying out of this resolution involves the adoption of 
* First Report of the British Association Committee on Units. 
