. _ C 437 ] 
furnifh me with an excellent clock, with a gridiron- 
pendulum adapted to it, executed by that diligent 
and ingenious artilr Mr. John Shelton. 
Dr. Bradley was pleafed to take upon him the 
trouble of betting the clock up at the Royal Obfer- 
vatory at Greenwich, and there to examine its going, 
where he informed me, that it loft 1 1 feconds per 
day, upon fiderial time, the thermometer of Fahren- 
heit’s conftrudion, which was placed within fide of 
the clock- cafe, {landing about 50 degrees, at a me- 
dium, during the time, in which the experiment was 
made. Though the contrivance of the gridiron- 
pendulum might be confidered as a fufficient fecurity 
againft any variations in the going of the clock, which 
might arife from the changes of heat and cold, yet it 
was thought the experiment would be more fatil- 
fadory, if the temperature of the air was let down at 
the time. 
Soon after my arrival at St. Helena, I fet up the 
clock in the valley near James’s Fort, in a place ele- 
vated 85 feet above the level of the fea. Being 
fenfible, how much the exadnefs of the going of a 
clock depends upon the firm manner of fetting it up, 
I. had large pieces of wood driven into a ftone-wall, 
between the joining of the ftones, to which I fcrewed 
the back of the clock-cafe, which w r as very folid and 
heavy, by four fcrews, the bottom refting upon a 
large flat ftone. The pendulum had not been taken 
off from the clock, for carriage, but was fecured to 
the clock-cafe, in order to prevent it from receiving 
any damage. A piece of wood was fcrewed to the 
back of the clock- cafe, having a round cavity in it 
before, juft large enough to receive the bob of the 
pendulum ; 
