Mr. Moon in Reply to Jesuiticus. 215 



expressly for Mr. Moon, but the instruction conveyed to him 

 through my short papers, was precisely that of which he ob- 

 viously stood in need. Instead of accepting this with thanks, 

 he ungratefully turns round and bites the hand that brings 

 him aid ; and, not content with this, he is ungenerous enough, 

 artd unjust enough, to say, that everything in those papers, 

 which is not erroneous, has already been given by himself! 



Belfast, February 9, 1846. J. R. YoUNG. 



[We omit the remainder of Mr. Young's letter, in which he animadverts 

 upori Mr. Moon in terms which the communications of the latter seem 

 well-calculated to provoke. The same discretion has been exercised with 

 regard to some parts of Mr. Moon's letter in the present number, as from 

 the character which the controversy has assumed, we are not disposed to 

 devote any more of our space to its continuance. — Edit.] 



XLII. Mr. Moon in Reply to Jesuiticus*. 



A FTER the notice which appeared in the last Number of 

 :**■ this Journal respecting his previous papers, there would 

 be an obvious impropriety in the writer of the following re- 

 marks attempting to force on the Editors of the Magazine any 

 matter which would tend to produce further discussionf on 

 the subject to which he has of late called attention, except so 

 far as he be driven to do so in self-defence. As, however, the 

 views to which the Editors afforded the means of publication 

 have been openly attacked in this Journal, their author con- 

 ceives he has a right to say a few words in their behalf. 



An anonymous writer, who subscribes himself Jesuiticus, 

 commences certain animadversions on my first paper on Fres- 

 nel's Theory of Double Refraction, by the remark, that " the 

 hypothesis on which FresnePs Theory of Double Refraction 

 is based is the following : — ' That the displacement of a mole- 

 cule of the vibrating medium in a crystallized body is resisted 

 by different elastic forces according to the different directions 

 in which the displacement takes place.' " 



He then proceeds to make some remarks on the reason- 

 ableness of this hypothesis, which it is not my present pur- 

 pose to dispute; but I must beg to observe, en passant, that 

 the above is not the hypothesis on which FresnePs Theory of 



* Communicated by the Author. 



+ We omit some portions of Mr. Moon's communication, where he ap- 

 pears to us to have lost sight of his declared purpose of confining himself 

 to self-defence, and has introduced matter " tending to produce further 

 discussion." — Ewt. 



