VOL. LII.] PHILOSOPHICAL TRANSACTIONS. 64C) 



On the 19th of July 17 63 we shall have an occultation of Antares by the 

 moon, on the '2d of November an occultation of Mars, on the 8th of September 

 one of Mercury: they will be very proper for determining the difference of longi- 

 tude between London and Paris. In 1764 there will be a still greater number. 

 But if you have an inclination to undertake a labour of this kind, you may meet 

 in the memoirs of the academy with occultations of stars observed at different 

 times, and find some corresponding ones made at London, whence you may de- 

 duce the difference of the meridians of these two cities, which we may be ashamed 

 to say we are uncertain of to 20^ For whether it be 9"^ 15^ or 9"^ 40^ is difficult 

 to determine : I mean of Paris and Greenwich. 



I beg you will answer for me the questions proposed to me by our worthy 

 friend Dr. Morton on the part of Mr. Dunn. 1 observed the exit of Venus at 

 Paris with a telescope of 18 feet, and an eye glass of '2-^ inches focus, and with 

 a smoaked glass which was sufficiently dark, but I was not uncertain so much as 

 a single second. M. Messier observed with a Gregorian telescope of I-l feet, 

 magnifying very nearly the same as mine, and he agrees very well with me. 

 M. Maraldi had a refracting telescope of 15 feet, but he was tired at the time ; 

 and M. de la Caille had a refracting telescope of M. Dollond's, which was not 

 well put together, and did not terminate objects distinctly. I took for the 

 moment of the contact the Jst instant of Venus's limb raising the sun's limb in 

 the slightest manner. The account of these obsei*vations will be in the memoirs, 

 of the academy for 1761, which is almost printed off. 



We reckon the longitude between Greenwich and Paris to be 9™ 20®: but I 

 do not know what are the observations upon which it is founded. The preceding 

 observations will contribute hereto. 



C. The Observations of the Internal Contact of Fenus with the Sun's Limb, in 

 the late Transit, made in different Places of Europe, compared with the Time 

 of the same Contact observed at the Cape of Good Hope, and the Parallax of 

 the Sun from thence determined. By James Short,* A.M., F.R S. p. 61 1. 



In the summer of the year 1760, the r.s. resolved to send some fit persons to 

 proper places of the globe, in order to observe the transit of Venus, which was to 



* Mr. James Short, an eminent optician and constructor of telescopes, was the son of a joiner at 

 Edinburgh, where he was born in 1710, and died at Newingtcn Butts, near London, in I76'8, con- 

 sequently at oS years of age. When 10 years old, his parents being both dead, he was placed in 

 Heriot's charity hospital at Edinburgh. Having manifested however uncommon talents for me- 

 chanics, &c. 2 years after, he was sent to the high school of that city, where he so much distin- 

 guished himself in classical learning, that his friends thought of qualifying him for a learned profes- 

 sion. After 4 years spent at the high school, in 1720' he entered as a student in the university of 

 Edinburgh, where he passed through a regular course of study; took his degree of master of arts j. 

 VOL. XI. * 4 O 



