REPEATING GONIOMETER. 



161 



brought to perfection without at the same time inducing 

 a corresponding amelioration in the latter. In propor- 

 tion as the crystal lographic ideas of Haiiy acquired more 

 exactness, it was found necessary to employ, for the meas- 

 urement of the angles of the crystals, methods of increas- 

 ing precision. 



Wollaston supplied this Avant by the invention of the 

 reflective goniometer which bears his name.* Malus 



hesitated fullj- to adopt the idea, after it had occuired to him as the 

 only mode of representing polarization, on the ground of being unable 

 to reconcile it with mechanical notions; and this more precisely as 

 to the notion of transverse vibrations alone being produced, which 

 constituted this theory in all its simplicity ; whereas Young had (as 

 we have just seen) believed both these and longitudinal \\hrat\ons to 

 coexist. To establish this point, he expressly says, was the main dif- 

 ficulty which embarrassed him.i — Translator. 



* The essential principle of the reflective goniometer of Wollaston 

 is extremely simple, and consists in this: a piece of crystal or any 



1 Ann. de Chimie, 1831, torn. xvii. p. 184. 



