211 



Reference to Plate III. 



Observations of the eclipses of Jupiter's satellites are the 

 most unsatisfactory which the practical astronomer is called 

 upon to make ; the immersions, however, will afford consider- 

 ably less incongruity than the emersions ; I believe much of 

 this may be attributed to the observer not having his eye well 

 directed to the spot at which the satellite first issues from the 

 shadow, for I have found that since a diagram, of which the an- 

 nexed is a copy, has been suspended in my observatory, the 

 discordancies have materially diminished. From experience, 

 therefore, I can recommend to others its adoption ; the observer 

 will also do well to prefix to the dates of those eclipses which 

 he is likely to witness, the planet's distance from opposition, he 

 will then immediately know which of the diagrams is most ap- 

 plicable to his purpose. The emersion may generally be ex- 

 pected a little to the north or south of the belts. 



Art. XIX. Observations on the Chronometrical Arrangements now 

 carried on at the Royal Observatory, under the authority of the 

 Lords Commissioners of the Admiralti/, tending to shew their 

 Inadequacy to the purpose for which they were designed. By 

 James South, F.R.S. 



Ix offering to the consideration of those who may feel an in- 

 terest in such matters, the following remarks, I trust, it will 

 be .believed that I am actuated by no sinister motive ; but con- 

 ceiving that the acts of public bodies, which have for their ob- 

 ject public benefit, when they have had not only notoriety, but 

 even national importance, attached to them, by insertion in the 

 London Gazette, become fair subjects for private as well as public 

 inquiry, I have resolved to investigate how far the advertise- 

 ment relative to chronometers, which appeared in the London 

 Gazette of June the 26th, 1821, is likely to prove beneficial to 

 the country. 



" Admiralty Office, June 25, 1821. 



" The Lords Commissioners of tbe Admiralty, being desirous of increas- 

 ing the number of chronometers for the use of his Majesty's Navy, and of 

 encouraging the improved manufacture of that important article, do 

 hereby give notice, that a dep6t for the reception of chronometers is 

 opened at the Royal Observatory of Greenwich, where the makers will be 

 permitted to deposit their chronometers, in order to their being tried, and 

 ultimately purchased for the use of the navy, or of being disposed of by 

 the proprietors to private purchasers. 



" And, for further encouragement, their Lordships will purchase, at the 

 end of each year, the chronometer which shall have kept the best time, at 

 the price of 300<., and the second best at the price of 200^, provided 

 that there have been aljove ten chronometers in the competition, and that 

 tbe said best chronometers shall keep their rates williin certain limits to 

 be bereafier stated. The other clironometurs their Lordships may pur- 

 chase, as they may think proper, at such sums as may be agreed upon 

 with the makers, and their Lordships h;tve reason to expect, that their an- 

 P 2 



