[ 266 ] 
TRANSITS compared with equal Altitudes, for finding the Error of the Merldiarx Mark. 
Tranfits of Sun at 
Noon per equal 
tranfit inltrument. 
altitudes. 
Differences. 
h > n 
h ' n 
// 
3 
4 45 9-3 
4 45 5>i 
4.2 W. 
1 1 
5 18 9,9 
5 18 7,3 
2,6 w. 
15 
5 34 43.9 
5 34 42>5 
1,4 w. 
18 
5 47 13.0 
5 47 io»3 
2,7 w. 
Mean difference 
2,7 Wefi. 
Hence it appears, that the Sun pafied at the tranfit inftrument too late 2",; by a mean of thefe 
obfervations, which (hews the mark was wert of the true meridian ; which gives the azimuth 
of mark, cr 50" fouth wcfierly. 
T R A N S I T of V E N U S, obferved at the N O R T H CAPE. 
1769 
T:* June 3 At 13'’ 46' 40" per clock, or 9'' o' 2", apparent time, the Sun came out from under 
a cloud, with V'enus on it, about |th of her diameter ; and at 14'’ o' 41" or 
9'’ 1 4' i", apparent time, Venus’s outer limb feemed to be in contafl with the 
Sun’s limb ; but no light of that part of the Sun’s limb could be feen, Venus be- 
ing apparently joined to the Sun’s limb by a black ligament, which gradually di- 
rainiflied in breadth; and at 14’’ 1' 36", or 9'' 14' 56", the Sun’s light broke 
through it, and Venus and the Sun were to appearance perfect (this was certain to 
about 10 or 15 feconds of time), and the black ligament contraded itfelf, fo that 
Venus was confiderably within the Sun’s limb, fuppofe ^Vth of her diameter. 
Turing thefe obfervations the air was red and hazy, and the Sun’s limb very tremu- 
lous, and the fpots in the Sun very indilHnd, and Venus feemed very ill defined 
when on the Sun. But a better idea will be formed of the bad appearance of Venus 
at the internal contad, owing to the very hazy Hate of the air, from the reprefentation 
of it, plate XIII. 
Here follow fome meafures I was able to take during the time the clouds were off the Sun. 
Time per 
Meafures of 
Meafures of 
clock. 
App. time. 
microm. in 
microm. in 
inches, &c. 
degrees, &c. • 
Soon after the internal contad, meafures of Venus’s diameter. 
0,1 
24 
0,1 
23 + 
0,1 
23— 
0,1 
22 -f 
0,1 
22 
0,1 
22 
0,1 
23 — 
0,1 
24 — 
0,1 
23 ^ 
0,1 
23 
0,1 
23 — 
0,1 
23 -^ 
0,1 
22, S 
Meafures of the Sun’s horizontal and vertical diamt 
taken immediately after Venus’s diameter. 
Mean 
Horizontal 
Diameter. 
Vertical 
4>9l 2l| 
23 
4 . 9 I 23 
4-9i 2ii 
4,8| 12 
4,8| 10 
4,8| II 
4 . 8 | 9 
4,9] 22,2 
3i'37",6i 
4.81 10,5 
Diameter. 
30' 
Mean of 
Difiei 
