primiitns SOM? © 249: 
firft conta&t, when not a fecond of its diameter had enter- 
ed upon the fun. It is moft probable that the zternal 
contact was pa{t before the thread of light appeared to 
me to be compleated. It feems as though fomething of 
the fame kind, muft alfo have been the cafe in moft of the 
European obfervations; as they make the ingrefs near a 
minute longer, than it was feen by moft of the American 
obfervers, when by theory it muft rather have been fhort- 
er. But the different appearances of Venus, different 
ideas of the contacts, with the unavoidable difference of 
eyes, telefcopes, the {tate of the atmofphere and the like, 
might eafily occafion fuch differences in the obfervations. 
Though in the fame circumftances, it can hardly be 
thought but that the Ewropean and the American obferva- 
tions would have more nearly agreed. 
An Account of the Tranfit of Mercury over the Sun, No~ 
_vember oth, 1769, as obferved at Salem, in Maffachu-- 
fetts; by the Rev. SAaMuEL WitiiAMs, A. M. 
THE tranfits of Mercury, though they are not of equal’ 
ufe in aftronomy with thofe of Venus, are yet of great ad—- 
vantage to perfect the elements of his theory, and to de- 
termine the longitude of places on the earth. I had an 
opportunity to obferve one of thefe tranfits, November 9, 
1769, in company with Andrew Oliver, Efg. at Salem. 
Mr. Oliver had a good reflector, magnifying about fixty 
times. But, his clock not being in fo good order as was 
to be wifhed, and not having any inftrument to take al-- 
titudes, I was obliged to have recourfe to the following 
method to determihe the time.. The day before the tran- 
fit | drew a meridian line, with which I examined the 
going of the town clock on the day of the tranfit, and on: 
the day after, and found it had kept time very well.. 
Comparing my watch with the clock, the time was point-- 
ed out to minutes pretty exactly. Taking the minutes: 
from: 
