CHRONOMETR Y. { 59 



was the cause of the suspension of this mercurial globule 



at the bottom of that fluid I repeated the experiments and 



varied it by substituting water, containing a certain 



quantity of gum arabic, in solution, in the place of pure 



water ; and I found in fact that much larger spherules 



were supported when the viscidity of the water was thus 



augmented. 



[To be concluded.] 



XV. 



Observations on some Errors contained in Mr, Thomas 

 Reitfs Papery published in the Journal of tlie last 

 Month, From a Correspondent *. 



As Mr. Reid^s paper inserted in the last Number of ^"*'^^^"<^**'^^* 



Mr. Nicholson's Journal, contains some statements which 1 



materially affect the history of chronomctry, but which, 



on referring to the original documents appear to be very 



incorrect, it seems proper not to lose time in rectifying 



'errors which otherwise might mislead such persons a^ 



have no opportunity or leisure to investigate the matter 



in question. 



The invention of the detached escapement Is one of the The Invention 



points the most satisfactorily ascertained in the progress escapement be- 



of time-piece making. It is clearly due to P, le Roy, longs to P. Ic 



who first produced an escapejnent of that sort, and pre- ^J^* 



sented it in 1748 to the Academy of Sciences at Paris; 



and his claim has never yet been disputed with any degree 



of reason, though considerable discussions have arisen 



respecting the pretensions of other artists who since the 



above date have thought proper to aspire to a shar^ in the 



same honour. The subject has been canvassed on several 



occasions, during the long interval of time which has 



elapsed since that epoch ; and every thing that could be 



said upon it seemed exhausted, till the present moment, 



when Mr. Reid, in a postscript to his paper, tells us, that ^^- ^^'^ ??• 

 AT rtM ' X • ,^.t . u V u J XI. 1 • X. r serts that Thi- 



Air. Ihiout m 1741 t published the description, of a out invented it 



before. 

 * Viz. the author of the Memoir at page 273 of our last Vol. 

 f The title of Thiout's work is, " Traite de I'Horlogerie me- 

 " chanique et pratique, approuvee par rAcadcmic Royale de« Sci- 

 " cnces." a vol. 4to. 



2 detached 



