18 ASTRONOMICAL AND- 
The angle BEH, in.a femi-circle, isa right-angle, / Eut. 31. 
III.) and HD, DE, DB, are three proportionals, / Euc.8. VI. 
that is to fay, HD: DE :: ED: DB. 
DE = 690. 2.838849r 
- x.3 
| | 5. 6776982 
HD . 322,3 2. 5082605 
BD = 1477,2 3 1694379 — 
| | HB— 1299,5 the micrometer meafure for the 
moon's diameter. It is a thing well known to mathematicians, 
that the fines of fmall arcs are nearly equal tothe arcs them- 
felves ; hence we havea rule to find the moon’s apparent di- 
ameter by proportions. 
O's micrometer meafure 1906, | Log.. 3.28or 
Itsz, SEPTA T SES LL 7517 
D's micrometer meafure 1799,5 _ $ 6° ar..6 7449 
Ds apparent diameter, 30° 6", ` j LL 7767 
Dedu& — 23 for the moon’s elevation. 
>’s horizontal diam. 29 43, but one fecond s more than what: 
is given from Mayer’s tables.. 
Mr. Brown and myfelf both noted the fame fecond for the: 
laft contact, which was at 2*53' 36” apparent time. There- 
were fome thin white clouds about the fun, yet I think the: 
obfervation was pretty good.’ 
69 0 | 
