John Arnold (watchmaker) wore it and carried it around. The watch exceeded all expectations, as it demonstrated great accuracy. The timekeeping error was 2 minutes 32.2 seconds, but the error in the last nine months amounted to just one minute. The greatest error in any 24 hours was only four seconds, or one nautical mile of longitude at the equator. Subsequently, Arnold produced a pamphlet that detailed the trial and results, with attestations of veracity from all those concerned with the tests. Maskelyne's assistant, the Rev. John Hellins, was in charge of the pamphlet. The astonishing performance of this watch caused controversy, because
Mean longitude angle between any physical objects. It is simply a convenient uniform measure of how far around its orbit a body has progressed since passing the reference direction. While mean longitude measures a mean position and assumes constant speed, true longitude measures the actual longitude and assumes the body has moved with its actual speed, which varies around its elliptical orbit. The difference between the two is known as the equation of the center. From the above definitions, define the "longitude of the pericenter" Then mean longitude is also Another form often seen is the "mean longitude at epoch", "ε". This