on the Planet Venus. 
207 
i2 h 3 6' 1st measure 44", 885 
2d 45 ,705 
3 d 45 ,104 
4th ■ 45 ,322 
5th 45 ,842 
Mean of the five measures 45",372 
Mean of the two sets 45", 623 
These measures were taken with a speculum that has been 
lately re-polished, and therefore required new tables for 
casting them up. Such tables were made by the following 
transits. 
Nov. 25, 1791. Transits of equatorial stars, taken to deter- 
mine the value of the micrometer, which is divided into re- 
volutions of sixty parts each. 
First set, 23", o 23,0 23,0 23,0 23,2 23,1 23,1 23,0 23,1 
23,1 = 23", 06 = 21 revolutions; correction -f- 7,2 parts, for 
zero and concave wires. 
Second set, 16", 8 16,6 16,4 16,5 16,7 16,6 16,5 16,8 16,4 
16,5= 16,58 = 15 revolutions 1,3 parts. Correction 7,2. 
By the first set, 1 part = o ", 272964 
Second set - - 273748 
Mean of the two sets o", 2 73356 
In the first set, the micrometer was opened to 21 revolu- 
tions ; and ten equatorial stars were observed to pass from 
one wire to the other. The opening was afterwards changed, 
and ten other stars were again observed to pass over the 
wires ; after which the micrometer was read off, and found to 
be 15 revolutions and 1,3 parts. 
2 E 2 
