414 PHILOSOPHICAL TRANSACTIONS. [aNNO I7I9. 



uin Observation of the End of the Total Lunar Eclipse, on the 5th of March 

 17 18, taken near the Cape of Good Hope-, serving to determine its Lon<^i- 

 tude. By E. Halley, R. S. Sec. N°36j, p. 992. 



It is now more than 30 years since I had a dispute with some of the 

 French Geographers about the longitude of the Cape ol Good Hope, said to 

 have been determined by the religious missionaries sent to China in the year 

 l685. By an emersion of the first satellite of Jupiter, they determined that 

 Cape to be 1^ 1 1"" or 174^° more easterly than Paris, that is 20° from London: 

 which for the reasons I then gave, I concluded could not be more than 1 7°. 

 See Phil. Trans. N° 185. Very lately I have met with an observation which I 

 believe will determine the controversy in my favour : for I had accidentally a 

 journal of an officer of the ship Emperor put into my hands, who in his return 

 from India, on the 5th of March 17^8, observed the end of a lunar eclipse, 

 when the visible altitude of the moon's centre was 13° 25', he being then in 

 the lat. of 34° 23' south, and as they found afterwards, just 180 leagues to the 

 eastwards of Cape Bonne Esperance. By calculation I find that in that lati- 

 tude the moon had that height at 7^ 174-'" p.m. and by comparing this 

 eclipse with that we observed with great exactness on Feb. U, l682, which 

 agrees perfectly well with our numbers, I conclude the middle of this to have 

 been at London at 3*" 48™. To which adding 1^ 46^" for the semiduration, the 

 end will be found to have been at London at 5^ 34"". The ship was therefore 

 in a meridian 26° to the eastwards of London: but she was at that time ISO 

 leagues to the eastwards of the Cape, which distance in that latitude gives 1 1° 

 of longitude; this therefore being deducted from the longitude of the ship, 

 leaves just 15°, or one hour, for the difference of meridians between London 

 and the Cape. So that by this account the Cape is yet nearer our meridian 

 than I had formerly made it, and near 6° nearer than M. de la Hire places it 

 in his Tables. 



On this occasion it may not be amiss to insert an observation or two I pro- 

 cured to be made at the Cape, by Mr. Alex. Brown, a Scotch gentleman, who 

 went to reside in India on our company's account. He carried with him a very 

 good brass quadrant, of above 2-foot radius, and at the Dutch settlement at 

 Table Bay, having rectified his pendulum -clock by correspondent altitudes, on 

 the 4th of August 1694. at 5^ 59"" man^, the distance of the bright limb of 

 the moon from the right shoulder of Orion was observed to be 25° 3'. And 

 the next morning Aug. 5, at 5*^ 21"^ 12% the same limb was distant from Pro- 

 cyon 25° 57', and at 5*^ 36"" 48' from the Lucida Arietis 58° 29'. 



It were much to be wished that the moon had, either of these mornings, 



