6p6 PHILOSOPHICAL TRANSACTIONS. [aNNO IjQs. 



from the observations made in Europe compared together ; but the observations 

 made at the Cape confirm it with the greatest evidence. 



It is of importance to be assured of the longitude of the places where the ob- 

 servations were made. M. W. endeavoured to determine them the best he was 

 able, by observations of the eclipses of Jupiter's satellites, made at the same places. 

 And he sets down a list of all the observations of these satellites made at different 

 places the last year. It is pity that Messieurs L'Abbe Chappe, and Rumoski, did 

 not succeed in observing several eclipses of the satellites, at Tobieske and Selen- 

 ginsk, the better to confirm the longitudes of those places. However it appears 

 that the difference between the meridians of Greenwich and Tobieske, is scarcely 

 more than 4^ 32™ 55*. That between the meridians of Greenwich and Selen- 

 ginsk, to judge from the 3 immersions observed there, should be but 7^ 6*" 0% but 

 from other considerations he thinks it must be 10 or 15"^ more. If the longitude 

 of these places should be more exactly determined, he is persuaded that we should 

 obtain the parallax of the sun to nenrly the Ipth of a second, so exact the obser- 

 vations made at Selenginsk and Tobieske and the Cape appear to be. 

 Mr. Planman at Cajaneberg, observed the transit as follows ; 



The beginning of the entrance at 3^ 59"^ 56^m 



Total immersion of Venus, or interior contact. ..... 4 18 5 



Second interior contact, or beginning of the exit. , . . 10 7 59 



Total emersion 10 26 22 



Mr. Planman made use of a telescope of 20 or 21 feet ; the latitude of Ca- 

 janeburg is 64° 13' 30'''; the difference of meridians between Greenwich and 

 Cajaneburg is sufficiently determined by observations on the eclipse of the moon 

 May 18, 1761, made at Stockholm and Cajaneburg. 



XVIII. Remarks on the Censure of Mercators Chart, in a posthumous fVork of 

 Mr. West of Exeter. By Mr. Samuel Dunn.* p. 66. Dated Sept. 4, 1762. 

 Mr. D. wishes to know if any paper has been printed in the Phil. Trans., 

 concerning a sphere being inscribed in a hollow cylinder, and swelling its surface 

 to the sides of the cylinder, thus to construct a more true and accurate chart for 

 the purposes of navigation, than that which was invented by Edward Wright, 

 and has long gone under the name of Mercator. The reason why he asks this 

 is, he says, because there is lately published a posthumous work of one Mr. 



* This gentieman was a native of Crediton, ia Devonshire, where he kept a mathematical school 

 for several years ; but afterwards removed to Chelsea, where he followed the same occupation. He 

 was well skilled in nautical calculations, and was a good practical astronomer. Beside.s several papers 

 inserted in the Phil. Trans., he was also the author of some .separate treaiises on mathematical sub- 

 jects, and published an Atlas in folio, which has been held in much estimation. He died in good 

 circumstances, and left an estate of about 30 pounds a year, to support a mathematical school in his 

 native town, the first master of which was appointed in 1793. 



