-C 505 3 
3. Mr. Rittenhoufe’s refra&or, with about the fame 
power, ufed by himfelf. 
Mr. Biddle had no telefcope ; but was very fervice- 
able in the other parts of the obfervation. 
Although there were many flying clouds, which 
frequently obfcured the Sun in the forenoon of the 
day ; yet from about one o’clock till half an hour pad 
three, the Sun fhone perfectly clear, and undirturbed 
by clouds j which gave us an opportunity, as favora- 
ble as we could wilh, for obferving the contacts, and 
making fome micrometer meafures. ' 
The firft external contact was obferved to the fame 
inftant by all the three obfervers,. who had no com- 
munication with each other, the two refra&ors being 
out of doors, and the refle&or within the obfervatory 5 
and the contacts noted (as at the tranflt of Venus) by 
lignals given to perfons fet at the windows of the ob- 
servatory, to count the clock. 
The contacts were as follows : 
1769, Nov. 9, apparent time. 
// 
At 2. 35 17 firft external contact, by all the three 
obfervers„ 
2 36 35 firft internal contact, by Dr. Smith and 
Mr. Rittenhoufe. 
2 36 33 firft internal conta< 5 t r by Mr. Lukens.. 
In. 20 th * £oo tbs ' " 
o’sdiam. per microm. 3 13 7 32 20,24 
Mercury’s diam. taken backwards and ’ 
forwards feveral times, and the fum J* © 8,22 
halved, gave only 
Vol. LX. Ttt No% 
