North Star, from tbe Pole the diftance of the Sights 
being made Radius, let the Stile be rivetted to the end 
of a ftraight Ruler ^ then when you would make ufe of 
it, lay the Ruler on an Horizontal Plane, fo that the 
end to which the Stile is fixed may over -hang, then 
look through the Eye-fight, moving the Inftrument till 
you fee the North Star appears to touch the circumfe^ 
rence of the hole in the other Sight, on the fame hand 
with the Girdle of CaJJiopea^, or on the oppofite fide to 
that whereon the Star in the Great Bears Rump is, at 
that time then draw a line by the edge of the Ruler, 
and it will be a true Meridian line, as 'tis very eafie to 
demonftrate. 
I do not hear that any of the Occultations oiAldeba- 
ran by the Moon were obferved laft year. I expefted 
feveral, but was always hindred by the weather from 
obferving any. I hope to.hav^ better. fuccefs this year, 
before the Moons vifible v/ay leaves that Star. 
, . A Note on this Letter bj the Pnbliper. 
It is very likely that the Black Wood, mentioned in 
this Letter is Oak, which has lain fo long as to be turn'd 
of that colour by the Vitriolick juices of the earth ip 
which it has lain, as galls and a folution of Vitriol turn 
of th^t colour. I never faw any Oak that had lain 
any time in any kind of earth, where water came to 
foakintoit, that was not turned of that colour : and I 
have feen many Trees of Black Wood of great bignefs, 
taken up fas well aslefler pieces) and all of it was Oak* 
It looks at firft taking up like Ebony, is very ponderous, 
but as it dries, it fplits, grows friable, light, and comes ^ 
to be good for little. 
E'R RAT Am No. ^6J. 
I)Ag. 71 ^ 1.33^1eg« definire : pag. 710.]. 13 - pro CorpufcUlif, lege qua- 
il corpufculis. 
Printed ^otSam. Smith' S^Timj . Walford y Printers to the Royal Socie^ 
ty, at iiiQ Prihccj Arm m St Pkuls Chtirdir-yard. 1701. 
