C 57} ] 
Readinefs, being the more defirous to make this Ob- 
servation, becaufe Mercury had never as yet been 
Seen entering upon or going off the Sun’s Limb at 
his defcending Node, and this Tranfit ought to be 
invifible to Europe. The better to obServe Mer- 
cury's Ingrefs on the Sun, I determined to make ufe 
of my 24 Foot Tube, while an Affiftant I had with 
me ufed that of Eight Foot : After which I propofcd, 
in order to find out his Path in the Sun, to obferve 
the Paflages of Mercury and the Sun’s Limbs by an 
horizontal and vertical Hair in the Telefcope of the 
Quadrant ; and I chofe rather to deduce Mercury’s 
Right Afcenfions and Declinations by Calculation 
from hence, than to obferve them immediately in 
the common way of placing one of the crofs Hairs 
parallel to the Equator, &c. becaufe, as the Sun was 
likely to be low before Mercury made his Entrance, 
Refraction would have caufed confiderable Errors in 
the Places of Mercury determined in this Manner. 
Having no Clock, I was obliged to make ufe of my 
Pocket-Watch, which I know to be a good one; and 
by this it was eafy to diflinguifli Time to a Quarter 
of a Minute, which would have ferved pretty well 
for the Ingrefs of the Planet. But as it was by no 
means Sufficient for thofe other Obfervations I 
defigned to make, I procured another Watch, which 
fhewed Seconds; and both thefe Watches I adjufted 
to the apparent Time, by feveral Altitudes of the Sun 
taken with the Quadrant before the Tranjit began ; 
and by Altitudes taken the next Day, I found that the 
Watches had kept time exactly enough. I expected 
that the Centre of the Planet would enter upon the 
Sun at 2 / j but, being apprehenftve that he might 
F f f f be 
