5QB PHILOSOPHICAL TRANSACTIONS. [aNNO I76I. 



pared to determine the time of the two contacts. Professor Zanotti, with the 

 telescope of the quadrant of2-i- feet focus. Professor Mathenci with the telescope 

 of 22 feet, and Signor Marini with that of 10 feet. 

 The internal contact was observed 



At 21^ 4"^ 34' with the telescope of 24- feet. 



21 4 58 10 



21 4 58 22 



TTie external contact was observed 



At 21^ 22'"30' with the telescope of 2-i- feet. 



21 23 O . . 10 



21 23 7 22 



During the intervals of the observations made with the quadrant, the planet 

 was always observed to be perfectly round, without any ring or nebulosity. The 

 author then proceeds to determine, by calculations, (the method of which he has 

 at large explained) the difference of longitude between the centres of the sun 

 and Venus, and also the planet's latitude. 



The following are the elements deduced from those observations, which were 

 made at the distance of at least an hour and a half. 



The horary motion of 9 in longitude 0° 3' 55'^'^ 



The horary motion in latitude O O 3()f 



The true time of the conjunction of and 9 18*^ 26™ OF 



The latitude of 9 at the conjunction 0° 9' 27^" 



From these numbers the author deduced the following elements, by trigonome- 

 trical calculations. 



The angle of the path of the ecliptic 8° 49' 23* 



The horary motion in the path 3 58f 



The part of the path between the middle of the transit and conjunction O 127 



The distance of the path from 0's centre southwards O 9 21 



The length of the path within the 0's disk O 25 29-j- 



The difference of longitude of and 9 at the ingress O 14 2 



The difference of longitude at the egress O 11 9-^ 



The latitude of 9 at the ingress south O 7 17 



The latitude of 9 at the egress south 11 12 



The time of the middle of the transit 18'' 4"^ 6* 



The ingress of the centre of 9 on the 0's disk 14 51 49 



The egress of the centre of 9 21 16 23 



It appears also by his calculation, that the time of the internal contact was 

 accelerated 30", and the last contact 18 ', by parallax. The internal contact there- 



