[ 401 } 



LXIV. Ohservat'wvs on M. Arago's *' Reclamation " respecting 

 liii Ocular Alicrurneler, publishtd in the Amiales de Ch.imie 

 ct de Physique. By the Rev. W. Pearson, LL.D. & F.R.S. 

 Treasurer of' the Astronomical Society, 



To Mr. Tilloch. 



Sir, — A FRIEND of mine has lately put into my hands one of 

 the numbers of the Annates de Cliiwie et de Physique (August 

 1820) imhiished by Messrs. Gay-Lussac and Aiago at Paris, iii 

 which number is contained a jjaper subscribed by the initial A, 

 tvhich makes an unwarranted attack on me, on the score of pla;- 

 giarism. 



At the first meetiiifi: of the Astronomical Society of London, on 

 March 10, 1S20, a Memoir of mine was read " On the doubly- 

 refracting Property of Rock-crvstal, considered as a Principle of 

 micrometrical .^{easurel^ents when applied to a Telescope ;" and 

 at the subsequent meeting on the lUth of April, a second Me- 

 moir by me was read " On the Construction and Use of a new 

 micrometrical Eye-piece of a Telescope," which Memoirs have 

 <iot yet l)een published; but the reports given of these in your 

 Philosophical Magazine, and in the Edinburgh Philosophical 

 Journal, have produced a belief in the mind of the writer A, who 

 can be no (Uhcr person than Mr. Arago of the Royal Observa- 

 tory of Palis, that an atteu'pt has been made l)y me, or by your 

 Reporter and Dr. Brewster's (who are unknown to me in that ca- 

 pacity ), to deprive Mr. Arago of the honour of ait original inven- 

 tion exclusively his own. 



Mr. Arago states as reasons for the publication of his Re- 

 clomalion, that he waited two moliths to see if the reports given 

 in the Piiilosophical Magazine' of June [or rather of March and 

 April] should be contradicted by me, and that he had forgotten' 

 my address, or he would have written to me on the subject of 

 my having claimed his invention of the rock-crystal micrometer; 

 he then proceeds to inform his scientific readers, that he became 

 acquainted wit!) me in London four years ago ; that in the sum 

 mer of 1^1!) 1 visited the Observatory of Paris, with a view of 

 learning the use of astronomical instruments {cjnelcjite Irarail as- 

 tronornifju':); to justify the choice that the Royal Society of Lon- 

 don, had prc\iously made of me as a memi)er; that he pointecf 

 out the observation of double stars as a proper object of luv re- 

 searches, which subject he says I had previously considered, hut 

 rould not pursue it on account of the defects in my micrometers;' 

 tliat he then showed me a particular iusirunient of his conlri- 

 Vauce, which he then applied to a telesco|)e by Lerebours, and 

 <vitli it determined the diameter of a ball which terminates the 

 • V(d.;i(.).No. 27-'. L>tc. li)20. 3 H steeple 



