POLARIZATION. 217 



ther, it is not only on account of its singularity that this 

 theory ought to command the attention of the physicist ; 

 Fresnel found it the key to all the beautiful phenomena 

 of colours, which are produced in plates of crystal pos- 

 sessing double refraction ; he analyzed them in all their 

 details ; he determined their most hidden laws ; he 

 proved that they were only particular cases of inter- 

 ferences. He thus overturned from their base many 

 scientific romances to which these phenomena had given 

 birth, and which had secured more than one pros- 

 elyte, whether by their striking nature or the distin- 

 guished merit of their authors. In a word, here, as in 

 every branch of science which is advancing towards per- 

 fection, the facts have seemed complicated only because 

 we examined them at too near a distance and with too 

 microscopic a view ; but at the same time, by a more 

 enlarged conception, their causes have been found to be 

 more simple than we might have expected. 



rOLARIZATION. 



Although I am aware at what point we risk tiring even 

 the most kindly disposed audience when we speak long 



at rif/lil angles to each other they could not. It only required then 

 the action of the analyzer (a) to resolve each vibration again into 



two, at right angles, of which two sets in a plane perpendicular to 

 that of analyzation are suppressed; and two in that plane transmit- 

 ted; and which., consequently, being in parallel planes, are able to 

 give interference, and produce the observed coloured tints. 



8KC. SEK. 10 



