IMPROVEMENTS IN CLOCK-ESCAPEMENTS. 419 



izing the force of the train is a remontoire in the train just below the scape-wheel, which is 

 then driven by a spiral spring or a small weight wound up at short intervals by the train 

 and the great clock-weight. The spring remontoire described in the supplement to my former 

 paper has been ever since used by Mr Dent in all his largest clocks. There are two of his 

 clocks in the same town similar in all respects, except that one has this remontoire and the 

 other has not ; and the clockmaker there who takes care of them both, and who has access to 

 a dipleidoscope for correcting them, reports that he finds it impossible to keep the one without 

 the remontoire to so good a rate as the other. Nevertheless a train remontoire, however 

 effectual in doing what it professes to do, cannot remove the friction on the pallets or keep it 

 constant; and it is subject to continual variation according to the freshness of the oil and the 

 temperature. In fact all that a train remontoire does for a large clock is to put it on a level 

 with an astronomical clock, of which the train is so highly finished that the force on the scape- 

 wheel has no sensible variation ; except that the long and heavy pendulum of the large clock 

 then gives it an advantage over the small one, and consequently turret-clocks with cast-iron 

 wheels can be made, by means of this remontoire, to go better than the best astronomical clocks, 

 provided the pallets are kept properly clean and well oiled. 



The result of all this evidently is that it is hopeless to expect any farther material im- 

 provement in clock-escapements in any direction, except that of materially reducing, if not 

 completely removing, the friction which affects the pendulum. And I shall now proceed to 

 give an account of the latest attempts that have been made in that direction — so far at least 

 as they appear to me to be worth notice ; for such attempts are being made every day, many 

 of them in ignorance of what is really wanted, and none of them with the slightest chance of 

 coming into general use. 



Until lately I thought that Mr Bloxam's escapement, which is mentioned in my former 

 paper and fully described in the Rudimentary Treatise on Clocks, was capable of satisfying 

 all the requisite conditions of a gravity escapement. But when it became necessary for 

 me to consider whether it ought to be introduced into the great Westminster clock, which 

 Mr Dent is making under the direction of the Astronomer Royal and myself, I found 

 that it could not be constructed so as to satisfy the proper mathematical conditions without 

 exposing it to such mechanical objections as would prevent its acting at all. In the only 

 specimen of it which (as far as I know) has ever been made, the scape-wheel lifts the 

 gravity arms, or pallets, through a very small angle, and therefore lifts them slowly, and 

 without giving them such a velocity as to carry them out so far that the tooth of the 

 scape-wheel can slip by instead of being caught and stopped : which is called trip- 

 ping. But if the lift is increased to anything near the amount which renders the escape- 

 ment independent of any moderate change of arc, it will be quite as liable to trip as 

 any other gravity escapement, and probably more, on account of the arms being lifted 

 with scarcely any friction. And therefore, although I believe that, even as it was made 

 by Mr Bloxam, it would go better than any dead escapement, because there is nothing 

 to cause any variation of the arc, still it cannot be regarded as a perfect gravity escape- 

 ment ; and it was also represented to me by those who are better judges of that point 

 than I am, that it would be too delicate and expensive to construct to be at all suit- 

 Vol. IX. Pakt III. 54 



