58 PHILOSOPHICAL TRANSACTIONS. [aNNO 1684. 



Concerniyig a Movement that measures Time after a peculiar Manner ; being a 

 Clock descendant on an inclined Plane. In a Letter from the Rev. Maurice 

 Wheeler, M.J. N" ]6l, p. 647. 



The exterior of this movement or clock, fig. 3, pi. 1, is a circular body of 

 3i inches diameter, consisting of 2 plates, measured by the same radius, and 

 fixed in a parallel position to each other by the hoop h, the breadth of which 

 is about an inch. This hoop and the two plates form the case of the move- 

 ment ; of which, the anterior plate is, towards the edge, inscribed with a 

 horary circle, the divisions of which answer to the hours of a natural day. The 

 deep shades within this circle are intended to represent a concave, of near half 

 an inch deep; and the prominence g, in the middle of this concave, is a hemi- 

 sphere of brass or silver, riding loosely on a pin, which lies hid, and is the axis 

 of the movement. The upper half of this hemisphere is hollow, but the lower 

 filled with lead ; and the small winged figure that sits on it, with an erected 

 finger performs the office of an index. But this being only for ornament, any 

 other index may be substituted for it, as fig. 4, provided the axis on which it is 

 supported, move freely in the hole H; and the lower part thereof, HI, so far 

 preponderate over HP, as always to keep the index pendulous, with its point to 

 the vertical hour. 



The manner of its motion, as far as it appears outwardly, is thus: SE, fig. 3, 

 represents a board or shelf, of a straight and even surface, about 6 feet long, 

 and so thick as not to be apt to cast with change of weather, nor to grow 

 camber under a small weight ; on this is the movement placed, and hereon to 

 perform its course, and therefore I call it the stage of the movement. This 

 stage is raised at the end S, about 10° above the horizon, or line of level HE; 

 but the angle of its declivity DEH, is variable. The two plates, which form 

 the case of the movement, are to extend all round beyond the hoop h, -f of 

 an inch, and the edges of them slightly indented ; that while the movement 

 descends upon the stage, it may turn only, and not slide. 



The use thereof in measuring time, is as follows. The movement being 

 placed as high as it can, near the point S, will move downward towards E, with 

 that slowness, as to finish one entire revolution in 24 hours; and while it does 

 so, the divisions on the horary circle, or dial-plate, successively culminating 

 over the point of the index, will show the hours of the day and night. For in 

 this movement, contrary to what is usual in othei-s, the hour is shown by the 

 access of the numbers to the index, which is always to keep the same position. 

 Now when by several repeated revolutions it has measured out the length of its 



