[ * 94 ] 
contact ; and, whilft I am very certain with refpedt to 
the particulars of the external contadt, cannot deter- 
mine why they differ from that ingenious obferver’s 
numbers, or any other’s. 
Samuel Dunn. 
*** When the limb of Venus was almoft clear 
of the fun’s difk, I perceived a difficulty would 
occur at the laft contadt, as the limb of the fun, 
and alfb that of Venus, which was to make the 
contadt appeared through a telefcope magnifying 220 times, the 
limits of time in which it continued in a like apparent ftate, by 
a telefcope magnifying | j times, may be fuppofed to have 
been j ^ j f eC onds of time j and as j * s 3 ®,, j weft: 
of Greenwich, the black contadt, by the above obfervation, with 
Mr. Short’s telefcope at Savile-Houfe 1 f 8 h 18' 18" 1 
the telefcope at Greenwich obfervatory J 18 18 58 J 
f Qh .O' J« I 
obfervations at thofe places being j ^ ^ j And, for other 
telefcopes, the limits above-mentioned may be fuppofed to have 
been nearly as in the following table. 
Magnifying power. 
Limits. 
200 times. 
3" of time. 
100 
7 
80 
8 
60 
11 
50 
*3 
40 
16 
35 
19 
30 
22 
25 
26 
OK) 
33 
»Q 
, 66 
lift 
