276 IMAGES >'ORMED BY CONVEX LENSES. 



The artificial This fubflance agreed, in all the properties which have beerr 



withTh^nTmral not ' ce d» witl1 tne magnetical pyrites ; and the precipitates ob- 



nugnetic pyrites, iained by adding pruffiate of potafh, and ammonia, to the 



muriatic and lulphuric folutions, were precifely limilar. The 



fpecific gravity was 4390, whilff. (as I have already remarked) 



thai of the magnetical pyrites is 45 18. 



(To be concluded.) 



XL 



Jnfiver to a Letter of C. L. with other Remarks, on the Images 

 formed by convex Lenfes. In a Letter from Mr. Ezekiei 

 Walker. 



To Mr. NICHOLSON. 

 Dear Sir, 



Remarks on the ^- L. >«> his letter in your laft Number, reprefents my firlt 

 Letters of C. L. p a p er as deficient in " philofophical correctnefs," and wanting 

 " the calm fpirit of philofophy." But in attempting to prove 

 my errors, he has proved nothing but his own want of know- 

 ledge: and to thofe who with to fee an example of C. L.'s 

 " culm fpirit of philofophy," I beg leave to recommend the 

 perufal of his letter in Vol. IX. p. 4J35, of this Journal. — 

 Thefe Grange afibr lions are followed by another itill more 

 Strange, 

 Quotation, in He fays, " / v:ill beg leave lo wave any attention to the 



which C. L. de- n ;ft or y f ^ r Walker's experiments upon which I have am- 

 ines Mr. W.'s y i . , • 

 foQ. St niddverfeo, and to deny fasjurfs. 



Thinking that I did not understand his meaning correctly, I 

 examined the iide-note, which runs thus: " C. L. declines 

 any further dilcuflion reipecting Mr. Walker's experiments 

 with lenfes, but denies the facli." 

 Mr. W.'s reply. As there is no reafoning with a man who will deny facts, 

 I (hail decline examining the remainder of C. L.'s letter. 



Your other anonymous correfpondent, who has denied Khc 



trull) of my experiments, will be more eafily anfwered. 



Horizontal The opinions which have been advanced refpecting the 



viofjit. horizontal luminaries, fince the days of Ptolomy, who was 



i>o;n about the year 70 of the Chriftian <ST3, are, fo numerous^ 



that 



