XLVII. (Supplement.) Ou Turret-Clock Remontoirs. By E. B. Denison, M.A., 



of Trinity College, Camhridge. 



[Read Fehruary 26, 1849.] 



I HAVE given above a general description of a remontoir escapement, and shewn its advantages 

 when properly made. But a remontoir apparatus may be introduced below the escape-wheel of a 

 common escapement, and will have the same effect as a remontoir escapement, except that it will 

 not remove the variable friction of the pallets, and will generally introduce some friction of its own. 

 For astronomical clocks, probably a remontoir escapement is the best construction. But there is 

 another class of clocks on which some attention has at last begun to be bestowed in this country, 

 and which, from the great length and weight that may be given to their pendulums, are capable, 

 when properly made, of excelling the performance of most astronomical clocks : I mean turret- 

 clocks. And these clocks require a remontoir more than all others, on account of the great in- 

 equality in the force of the train, arising from the varying friction of the very heavy machinery, 

 and the occasional exposure of the oil to a freezing temperature, and the action of the wind on 

 the hands. 



Now any remontoir escapement, to satisfy the condition which I have shewn ought to be 

 satisfied by them, will require great accuracy in its construction, and will be too expensive to 

 have any chance of being generally adopted. Moreover, there are two other conditions which a 

 turret-clock must satisfy, in order to be of any use as a public regulator of other clocks; viz. that 

 of striking the first blow at exactly tiie proper second, and that of enabling people to distinguish 

 every twentieth or thirtieth second by a quick and visible motion of the minute-hand only at those 

 intervals. These conditions were laid down by the Astronomer-Royal for the Royal Exchange 

 Clock, and are also proposed by him for the great Clock for the Houses of Parliament. And these 

 conditions, especially the second of them, can only be satisfied by introducing a remontoir into the 

 train somewhere between the dial-work and the escapement. In the Exchange Clock a small weight 

 is raised by a wheel with internal teeth at every twentieth second : in some French turret-clocks 

 the weight is raised in a somewhat similar manner by two bevelled wheels : in a clock put u]) 

 in Edinburgh in the last century, mentioned by Reid in his book on Clock-making, tl)ere was 

 an endless chain remontoir (which has also been attempted again in France) ; but it was removed 

 on account of the rapid wearing both of the chain and the letting-off pins. But for tliis, and 

 the variable friction of such a chain, that kind of remontoir is probably the most tempting, as 

 it is the most simple, of the gravity remontoirs. Both the other constructions are com])licated 

 and expensive, and have a good deal of friction of their own ; and though I think a dillcrent 

 kind (jf gravity remontoir may still be made, more simple and quite as effective (iviiich however 

 I shall not stay to describe), I am inclined to propo.se a spring remontoir as superior to any 

 gravity one, on account of the greater facility of its construction, and the unusual circumstance 

 of its being possible totally to exclude friction in its application ; and I may also mention, as an 

 incidental advantage, that it possesses a sort of natural coinjiensalion, the spring being stronger 

 in cold weather, when the oil on the pallets is less fluid, and tiiiivfore a grniter niaintiiining 

 force is required. I find indeed that a sj)ring remontoir is not mw, having been tiiiil in I'rance, 



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