VOL. LXI.] PHILOSOPHICAL TRANSACTIONS. ,1^5 



hence the daily rate of the clock's losing on mean time, by a mean of 40 results, 

 is 20.8 seconds. By the first and last days observations compared together, the 

 clock lost IQ"" 49'.9 on mean time in 57 days, which is at the rate of 20^88 or 

 20'.9 per day. The swing of the pendulum on each side of the perpendicular 

 during this time, varied between 1° 50' and 1° 55. 



Remark. — ^The same clock, when fixed up at the Royal Observatory at Green- 

 wich, before the voyage, with the pendulum of the same length, got at the rate 

 of 1"" 45.8^ per day, on mean time, between April IQ and July 18, 1768. 

 Therefore the force of gravity at Greenwich is to that at King George's Island, 

 as 1000000 to 997075. N. Mashehjne. 



Next follows a series of observations of meridian zenith distances of the sun 

 and fixed stars, for finding the latitude of the observatory: from which it is 

 found, that the mean of all the results from the sun and six stars to the North, 

 gives the latitude 17°28'5l"s; and the mean of all the results from the stars 

 to the south, gives the latitude 17° 29' 38" s: the mean of these two means is 

 17" 29' 15" s. which may be taken for the latitude of the observatory. 



Remark. — It must be confessed, that the results of these observations (most 

 of which were made by Mr. Green) differ more fi*om one another than they 

 ought to do, or than those do made by other observers, with quadrants of the 

 same size, and made by the same artist, the cause of which, if not owing to want 

 of care and address in the observer, I don't know how to assign. N. Mashelyne. 



The next is a series of lunar observations, that is, of the moon's distances 

 from the sun and stars, for the longitude; the mean from all these give the 

 longitude of the observatory, on George's Island, 149" 36' 38" west of Green- 

 wich observatory. To these succeed a set of observations of the eclipses of 

 Jupiter's satellites, for the same purpose; from which it is inferred that the lon- 

 gitude of the same place is 149° 32' 30". 



Next, the observations of the main object, the transit of Venus, is given at 

 considerable length, by the different observers. And, 



1st. By Mr. Green, with a reflecting telescope of 2-feet focus, magnifying 



power 140 times. 



Apparent time. 

 June 2. 

 Light thus on the O's limb, pi. 4, fig. 1 21'' 25"" 40* 



Certain, as in fig. 2 21 25 55 



First internal contact of $ 's limb and the ©, fig. 4 21 43 15 



Penumbra and ©'s limb in contact, fig. 5 21 43 55 



First contact of penumbra, undulating, but the thread of light June 3, 



visible and invisible alternately 3 14 3 



Second internal contact of the bodies 3 14 51 



Second external contact 3 31 28 



Total egress of penumbra, ©'s limb perfect 3 32 14 



