88 Sir George Shuckburgh's Account 
same language. For this purpose the vibrations of the pen- 
dulum are only y of a common pendulum, = 10" of space ; 
and the index that is carried round immediately by the pen- 
dulum, viz. on the same arbor with the pallet wheel, in one 
revolution describes 10' of sidereal space ; the next index from 
the centre of the dial plate shews the degrees, and every 10th 
minute, making one revolution in io°. And lastly, the de- 
cades of degrees, from 1 to 3 6, = 360°, are shewn through an 
opening in the dial plate, which in some clocks is ap- 
propriated to the day of the month. But perhaps this will 
be better seen from inspection of the plate (Tab. XII.) 
wherein the hands are so placed as to indicate 147 0 14' 10". 
The small hand (it may be perceived) has two sets of figures 
round its circle, the one shewing the minutes, and every 10th 
second, the other the number of beats from o to 60, and this 
latter enumeration is what alone can be attended to in the 
observations ; that is, the degrees and every 10th minute are 
set down in the journal immediately from the indexes, and 
the subdivisions below io' are set down in beats of the pen- 
dulum, reckoning from o to 60, and reduced afterwards at lei- 
sure. The pendulum, only 1 7 inches in length, is a compound 
gridiron composed of 5 rods, of which 3, viz. the centre and 
two exterior, are of iron, and the two next to, and on each 
side of the centre, are compounded of silver, brass, and zinc. 
The weight of the pendulum ball is about 6 pounds, and that 
of the clock weight 32. The spring, by which the pendulum 
is suspended, is said to be so constructed as to produce cy- 
cloidical arcs of vibration ; but my reliance upon this con- 
trivance is not very perfect. The two chief arbors are 
jewelled, the pallets are rubies, and the axis of the principal 
