Rqt/al Astronomical Society. 305 



is an opening showing the Herschel mark, designating the site of 

 the 20-feet reflector. The opening will be closed with a bronze 

 plate, containing the inscription of the purpose for which the obe- 

 lisk is erected." 



VI. On Loud Beats of Clocks used in Observatories, Ey J. S. 

 Eiffe, Esq. 



This paper gives an explanation of a simple and easily applied 

 method of obtaining very loud beats for the astrononiical clock. 

 The author alludes to the difficulty which has been hitherto experi- 

 enced in obtaining any sound in the beat of astronomical clocks at 

 all approaching that which is necessary for distinctness under ordi- 

 nary circumstances. He then adverts to the necessary irregularities 

 in the clocks of the ordinary construction, arising from the large- 

 ness and imperfection of the workmanship of the brass-work, and 

 hints at a method which he has debased, whereby the present large 

 circle of seconds can be retained with a small and delicate move- 

 ment, such as those used in marine chronometers, and without any 

 intermediate wheel. 



But without a method to enable the observer to increase at plea- 

 sure the loudness of the beats, it is manifest that the beats of such 

 a clock would not be loud enough for the ordinary purposes of an 

 observatory ; and the author's invention, described in the present 

 paper, is intended to supply this deficiency by the introduction of an 

 apparatus to produce loud beats simultaneously with the escape of 

 the seconds' wheel from one pallet to the other, which is totally in- 

 dependent of the size and weight of metal of the works of the clock. 

 The mode of constructing the apparatus is as follows : — 



Two pieces of thin brass are placed at the sides of the frame- 

 work of the clock, in length the same as the space between the pil- 

 lars ; in width, about two inches or more at pleasure ; these pieces 

 of brass are placed horizontally, at about the same altitude from the 

 base as the axis of the escape-wheel pinion, and at right angles to 

 it, or nearly so. They should be made of such a size as would en- 

 sure a sound, distinct, sharp, and short. The little tables can be 

 made to any size, as is mentioned above. Upon these tables or 

 plates two hammers ply, supported by arbors at the same elevation 

 as all the others. The pivots should be made small for easy motion. 

 The hammers are intended to beat upon the middle of each brass 

 table simultaneously with the drop proper of the escape- wheel ; 

 through the agency of the pendulum, they are lifted alternately by 

 the heels of the anchors of the pallets, assisted by a passing spring 

 similar to that used in the chronometer escapement. It has just 

 been observed, that the arbors which support those little hammers 

 are placed at the same elevation from the base of the brass frame- 

 work of the clock as the escape-wheel arbor, but at the sides, and as 

 near to the edge as possible. About the centre, or midway between 

 them, are afiixed brass collets, about 1-8 of an inch in thickness, 

 and 1-4 of an inch in diameter. Two slender pieces of spring are 

 secured to the collets by screws passing through square holes formed 

 longitudinally, to secure power of adjustment for bringing the arms 

 into proper contact with the anchor of tlie pallets. The little ham- 



Phil. Mag. S. 3. Vol. 25. No. 166. Oct. 1844. X 



