Given the task definition and input, reply with output. In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.

John Harrison:  I may not be spared to complete another watch , but I 've begun _ one _ . It will not , gentleman , be a copy , because I am mindful of the Act of Queen Anne , to which I 've clung for over 50 years like a , like a shipwrecked sailor to a barrel -- " to be practical , " and that 's been my gospel and my creed . I have an idea that the heat compensation must be within the balance of the watch and not around it . And this morning I made this.[He shows a heat - compensated balance wheel . I tried the idea in my first sea clock , over 40 years ago . I failed . I did n't undertand it ; so much I did n't understand . A compensating balance wheel will simplify the adjustment of the machine , so others may make my watches more easily ... should God grant me the time to complete my labours .

watch