124 



HOROLOGY. 



Description 

 of the re- 

 montoir 

 which was 

 applied to 

 the dock 

 of St An- 

 drew's 

 Church, 

 'Edinburgh. 



toirs* that is, that the movement should at intervals be 

 made to wind up either a small weight, or bend up a 

 delicate spring, which alone should give its force to the 

 'scapement, by which means the pendulum or balance 

 was supposed to be always impelled by an equal and 

 uniform force. The earliest thing of this sort was used 

 about the year 1600. Huygens applied it to some of his 

 clocks, and gives a description of it in his Ilorologium 

 Osc/llalo>itttn ; and Harrison had one in the marine 

 timekeeper, which gained him the great reward. We 

 are of opinion, that they are of no great use either to a 

 clock or a spring time-piece; for if the pendulum of the 

 one is well fixed, and the momentum of the ball is not 

 too little, any small inequalities of the motive force 

 through the wheels will hardly be perceptible; and in 

 the spring time-keeper, the isochronism of the pendu- 

 lum or balance spring is sufficient to correct any ine- 

 qualities whatever in its motive force. As their me- 

 chanism, however, is curious, and has been rarely de- 

 scribed, it may not be uninteresting to our readers to 

 have such an account of it as would enable them to 

 make and adopt it should they think it proper. 



The one which we propose to describe, is that which 

 was contrived by Mr Reid for the clock of St Andrew's 

 church. Suppose a small frame, separate and indepen- 

 dent of the clock frame, to contain two wheels, one of 

 which is the swing wheel, having within it the 'scape- 

 ment work. The other wheel is crossed out, so as to be 

 as light as may be, the rim being left just so broad 

 as to admit fixing on it seven kneed pieces or teeth, 

 each about a quarter of an inch thick and half an inch 

 long, three of which are on one side of the rim, and four 

 on the other side. Three on each side have the knees 

 of different heights, corresponding each to each. The 

 fourth is a little higher than either of the third highest. 

 The wheel on which these are fixed, has a tooth pro- 

 longed beyond the rim, of the same thickness and length 

 as the others, making eight teeth in all, having a small 

 space left between each. These teeth become as it were 

 so many wheels in different planes, and are at equal dis- 

 tances from one another, with the same extent of radius 

 coming to the centre of the swing wheel arbor, being 

 just so much larger than that of the swing wheel, as to 

 allow the swing wheel teeth to clear the arbor of it. 

 The edge or side of the teeth which rest on the swing 

 wheel arbor is a plane, and rounded off on the opposite 

 side, to the point or angle formed by this plane. The 

 arbor of the swing wheel has eight notches cut into it 

 a little beyond the centre. These correspond to the 

 eight teeth of the other wheel, and are sufficiently wide 

 and deep to allow the teeth to pass freely through them. 

 Each notch stands at an angle of 45 degrees to the one 

 which is next it, which difference is continued along 

 the arbor through the whole, making 360 degrees for 

 one revolution of the swing wheel. On each of the ar- 

 bors of these wheels was fixed a pulley having a square 

 bottom, in which were set about ten hard tempered steel 

 pins a little tapered, something like the pullies at the 

 old thirty hour clocks, whose bottom was round in place 

 of square. The pendulum was fixed to the wall of 

 the steeple, as well as the frame containing the 'scape- 

 ment work, and the apparatus which has been descri- 

 bed. The arbor of the eight toothed wheel had one of its 

 pivots prolonged with a square on the end outside. The 

 clock frame containing the movement was in the cen- 

 tre of the steeple, and the pinion in it, which suppose 

 to be that of the swing wheel, had one of its pivots also 

 prolonged, and squared outside. These squared pivots 

 were connected by a steel rod and Hooke's joints. The 



main weight of the clock being put on, must urge not 

 only the wheels to turn, but that of the wheel having the 

 kneed teeth ; but some one or other of these teeth pres- 

 sing on the arbor of the swing wheel cannot turn, con- 

 sequently none of those in the large frame can turn, 

 nor can the swing wheel turn here unless some other 

 means are used. An endless chain was provided, and 

 passed over the two pullies fixed on the wheel arbors, 

 and through two common pullies, to one of which is 

 hung the small weight which is to turn round the swing 

 wheel, and to the other a counter weight. The 

 weight which turns the swing wheel, has its force 

 placed on that side so as to make the wheel act proper- 

 ly with the pallets; now, while the swing wheel is turn- 

 ing, (the pendulum being supposed in its motion,) one 

 of the other wheel teeth is gently pressing on its arbor. 

 Whenever this tooth meets with its own notch, it will, 

 by means of the main weight, be made to pass quickly 

 through it ; while passing, the small weight is wound 

 up a little by the main one; the succeeding tooth then 

 meeting with the swing wheel arbor, rests on it for a 

 quarter of a minute, till its notch comes- about ; it then 

 passes in its turn, and so on. The swing wheel makes 

 a revolution every two minutes, in which time the 

 wheel with the eight teeth makes also one. The mi- 

 nute hand, by this mechanism, when passing one of the 

 notches, makes a start every quarter of a minute ; at 

 every such passing, the small weight is wound up a lit- 

 tle by the great or main one. After the clock had gone a 

 considerable time with this, it was found that the kneed 

 teeth got a little swelled on their parts of rest, by 

 the force of the main weight which made them fall 

 on the swing wheel arbor. To remedy this, an endless 

 screw wheel was put on the arbor of the remontoir whee}, 

 (or wheel with the kneed teeth,) working into an upriglrt 

 endless screw, on the upper end of whose arbor was 

 fixed a pretty large fly, in order to lessen the velocity of 

 the remontoir wheel, and make the kneed teeth fall 

 gently on the swing wheel arbor. This helped the 

 swelling greatly, but did not entirely prevent it, though 

 it existed now in a less degree. The endless chain had 

 also a tendency to wear fast; in consequence of this, and 

 of no provision having been made for the swelling of the 

 kneed teeth, by making the notches on the swing 

 wheel arbor much wider than was required for them 

 when newly finished and first applied, this part of the 

 remontoir was taken away, and the rod, with Hooke's 

 joint, was put on the square of a pivot of the swing 

 wheel prolonged on the outside of its frame. These 

 matters being guarded against, it might be well for 

 some artist in future to try such a remontoir. During 

 the four years it was in use, the clock went uncommon- 

 ly well, and was the admiration of a gentleman who 

 lived opposite the church, and who was an amateur in 

 horology. One of Mr Reid's men who took an interest 

 in this clock, said it did not do so well after the remon- 

 toir was taken away. This, however, may have been 

 more owing to a change in the position of the weights, 

 than to any thing else, occasioned by a chime of eight 

 large bells being put up in the steeple. For the weights, 

 in place of having their natural fall, were carried a great 

 way up in the steeple above the bells and clock, in order 

 to fall down again ; and here a complication of rollers 

 and pullies became requisite. 



Harrison's remontoir is a very delicate spring, 

 which is bent or wound up eight times in a minute. 

 Were it necessary, a more obvious description could be 

 given of it than that which is given with his time- 

 keeper. In Haley's, the remontoir spring is bent up 



Escape- 

 ments. 



Description? 

 of the re- 

 montoir 

 which was 

 applied to 

 the clock 

 of St An- 

 drew's 

 Church, 

 Edinburgh.. 



Jlarrison's- 

 remomoir. 



