NAVIGATION. 37 



" or nominate for the experiment, without losing 

 " their longitude beyond the limits before 

 " mentioned." l 



After first completing a chronometer in 1736, 

 Harrison offered a chronometer to the commis- 

 sioners for this prize, which, tried " in a voyage to 

 Jamaica in 1761-62, was found to determine the 

 longitude within 18 miles ; he therefore claimed 

 the reward of 2O,ooo/., which, after a delay caused 

 by another voyage to Jamaica, and further trials, 

 was awarded to him in 1765 io,ooo/. to be paid 

 on Harrison's explaining the principle of con- 

 struction of his chronometer, and io,ooo/. whenever 

 it was ascertained that the instrument could be 

 made by others. The success of Harrison's 

 chronometer is owing to his application of the 

 compensation curb to the balance-wheel, and on the 

 same principle he invented the gridiron pendulum^ 

 for clocks. These, along with his other inventions, 

 the going fusee, and the remontoir escapement, 

 were considered to be the most remarkable im- 

 provements in the manufacture of watches of the 



1 Extract from Act of Parliament passed in 1714. 



