X)F THE LATE PROFESSOR ROBISON. 503 



Other respects, that was now submitted to examination. It« 

 was intended that Mr Robison should accompany young Har- 

 rison and the tixne-keeper, in a frigate, the Deptford, to Port 

 ■JRoyal in Jamaica, in order to determine, on their landing, the 

 difference of time, as given by the watch, and as found by as- 

 tronomical observation. The time-keeper, accordingly, was 

 put into the hands of Mr Robertson, of the Naval School at 

 Portsmouth, who determined its rate, from nine days that it 

 remained in his custody, to be 2f'^<^- slow, per day, and also, 

 the error to be 3^^- slow, on the 6th of November, at noon, 

 according to mean solar time. 



The Deptford sailed on the 18th of November, and arrived 

 at Port Royal on the 19th of January ; on the 26th, Mr Robi- 

 son observed the time of noqn, and found it to answer to 

 4h. 59m. 71 sec. by tjjg watch, and this being corrected for the er- 

 ror of three seconds, and also for the daily accumulation of 

 2j'«=- for eighty-one days five hours, the interval between the 

 observations, the difference of longitude between Portsmouth 

 and Port Royal came out 5^- 2™- 47'^'^ ; only four seconds less 

 than it was known to be from other observations. 



The instructions of the Board farther required, that, as soon 

 as an opportunity could be found, the same two gentlemen 

 should return with the watch to Portsmouth, that, by a com- 

 parison of it with the time there, the total error, during 

 both voyages, might be ascertained. The opportunity of re- 

 turn occurred sooner than they had any reason to expect ; for 

 the Spanish war having now broke out, an alarm of an inva- 

 sion of Jamaica from St Domingo, occasioned the Governor to 

 dispatch the Merlin sloop of war to England, to give intelli- 

 gence of the danger. Mr Robison and Mr Harrison obtain- 

 ed leave to return in the Merlin, and sailed on the 28th, ha- 

 ving been but a few days in Jamaica. This voyage was an 



3 S 2 epitome 



