384 INVENTION Of THE BALANCE SPRING, 



who wish to see more oi; the subject of the isochronism of 

 pendulum springs, and of detached 'scapements, may con- 

 " "stilt his Trakd des Horlogcs Marines, published in 1773, and 

 the SuppUment au Traite dcs Horhges Marines, published iu 

 1787. There is, in Thiout, an idea of a sort of detached 

 'scapement; this work of his was published in 174'2. 



In M. Berthoud's SuppUment, he says, " Such are the ob-> 



*' servations which I made the I7th of March, 1763, in com- 



" posing my first astronomical watch, which was finished 



" about the beginning of 1764, the designs and the desciiption 



" of which were lodged with the Academy in August r764'." 



" See Traite des Horhges Marines, Append, page 533." " 1 sold 



*' this watch, when in London, in 1766, to Mr. Pinchbeck, who 



** purchased it for the king of England : it was the first pocket 



*' watch that had been made in Europe having a compensation 



" for heat and cold." 



te Roy's ba- M. Le Roy, in his Mesure du Temps en Mer, gives the drawing 



lance of com- ^f ^ compensation balance, which is the first,* as it were, that I 



Ed partsf^ have seen or heard of, the idea of which he confesses to have 



taken from Mr. Harrison's compensation bar. But the invention 



of the compensation balance itself is due to Mr. Harrison, which 



— is presumed may be presumed from what follow^: " You will now permit 



to have been «< . }^ ^ ^^^.^ oj. j^q as to the compensation for heat 



previously ^ ^ . , ■ • 1 ^111 1 • i 



made by Har- " and cold in the balance. It is the original method by which 



rison. a jy^^^ Harrison attempted to correct the error, which, as he 



" was pretty tenacious of his own opinion, he carried into exe- 

 " cution contrary to the advice of Mr. Graham, but found, 

 "* by experience, that Mr. Graham was right, and was forced 

 «* to throw it all away, t a»<i to contrive his method of apply- 

 " ing it to ihe balance springs." See Mr. Mudge's Letters to 

 Count Bruhl. 



Great merits of And farther, in honour of our country, it must be acknow- 



Arnold. 



* I suppose this expression to imply the compensation balance 

 df two metals, in contradistinction to the fluid thermometer ba- 

 lance, which has no relation to Harrison.— N. 



t The late Mr. Arnold, by making the compensation in the ba- 

 lance, and by its being now carried into general practice, and, as 

 it were, confirmed, proves that Mr. Harrison's original idea was 



good. 



ledged 



