S I R, 



B, 



On tie Efcapements of Time Pieeet, te 



IV. 



0« the Efcapements of Time Pieces. By Mr, TaOMAS Rejd. 

 To Mr. NICHOLSON. 



Edinburgh, Jpril 6, l80l. 



^EING lately favoured (by a friend, and one of the moft eminent philofophers of this 

 place) with a reading of your ufeful Journal, chiefly with a view that I might fee the ac*- 

 count given of Mr. Prior's efcapement, in which I was fomewhat interefted, having made 

 one of the fame kind in the year 1793, and which watch is at prefent in the hands of Mr. 

 Howells, Na. 15, White Hart Row, Kennington Lane, Surry. 



The originality of invention that feems to attach to Mr. Prior, I lay no claim to; as by 

 a note it appears that he had not feen the efcapement of Mr. Mudge, and I may add, nor 

 perhaps that of Lepaute's. Although I had not feen Mr. Mudge's efcapement, fome 

 hints refpedting it were given me in an obfcure manner, but yet fo as by them I could com- 

 prehend it. The efcapement of Lepaute's I was perfe£l:ly acquainted with ; and it was in 

 attempting to combine his with Mudge's that led me to make the one now in queftion. 



In mine, the time of reft of the teeth, and the flanch for the impulfe, is on the infide of 

 the pallets ; and in that of Mr. Prior's they are on the outfide. 



There is a very material circumftance which Mr. Prior has not perceived. His pins are 

 arranged in the fame line of circle on both fides of the wheel. This will make a confider- 

 able difference, efpecially if the pins (hould be left pretty thick, which will be the fame as 

 if the pallets were impelled by wheels of unequal diameters, and they will confequently 

 receive unequal impulfes. 



That pallet which moves inwards, receives its impulfe from the outward part of the pins. 

 The pins ought to be fo difpofed as to give equal impulfes. For that purpofe, let a very 

 fine circle be traced on the fide of the wheel, let the holes for the pins, that are to z£t on 

 the pallet outwards, be drilled infide of the circle, and.fo as that the edge of the holes fliall 

 coincide with it; thofe pins for the inward pallet muft be drilled without the circle, and to 

 have the edge of their holes alfo to coincide. In this cafe, the impulfe given to the pallets 

 will be equal ; but then it may be faid that the reft is not equal, this laft is fo trifling, that 

 of evils it is the \effeu 



Ih this cafe of an efcapement wheel with pins on each fide, the impulfes and times of 

 reft are brought nearer to an equality than in Mudge's, yet his teeth have fome advantages . 

 which the pins want. 



The roller attached to the verge, and ferving as a pallet, Is not new. Le Roy, Berthoud,. 

 and others, had ufed fuch, nor do I fee much benefit to be derived from it. The watch- 

 makers of Chaux de Fonds, Lode, and of Geneva), think fo little. of this, that. they ufe- 



- fimply/ 



