Trial of H.4 to Jamaica
Chapter 11, Trial of H.4 to Jamaica, p. 100.
To qualify for the highest award of £20,000, the timekeeper would have to show that on arrival in Jamaica it had not exceeded a total loss or gain of 1 minute 54 seconds of time since it had been set by Mr Robertson at Portsmouth on 7 November, some 81 days previously. This performance would be the equivalent of a variation of under 1 1/2 seconds a day, a standard of timekeeping which, even to-day,could be achieved by very few high grade watches. (Note : A watch is 99.99% accurate if it gains or loses no more than 8 seconds a day.(There are 86,400 seconds a day, ... 8sec./day=less than 1 in 10,000=less than 0.01% error, or >99.99% accuracy))
John Harrison, The Man who found Longitude, Dublin: Made and Printed in the Republic of Irland by Hely Thom Ltd.
"This book tells the story of how Harrison succeeded in doing the near-impossible by designing and constructing a marine time-keeper that met the onerous conditions laid down; and then how he had to contend with a series of official investigations, interminable delays and frustrations before he received his deserved reward"
- The Longitude Found, D.H. Sadler, Reviews no 3, Vol 20, pp. 358-360. (journals.cambridge. org)