MicrocGRaPHta. 
if therefore we would come to aity certainty in this point, we multge 
other wayes to work 5 and asI have bee ehaningdthn ciel am, 
Give property of the Air by other, wayes the are, wual, foimuftwe 
find the Parallax of the Planets by wayes not yet ‘practifed > and to ai 
end, cannot imagine any better way, thenthe Obfervations of thes b 
two perfons at very far diftant parts of the Earth, that lye as feekas my 
ok 
be under the fame Meridian, or,Degree of longitude , but differinig-as 
muchin latitude, as there can be ae eocesiehdae toa : Tee 
-perfons, at certain appointed times, fhould (as ne — 
atthefamietime, obferve the way of the, Alvony Afars,. Venus, “Fapiter, 
and Saturn, amongft the fixt Stars, witha good large Telelcope, , and. mar 
king little-Iconifmes, or pictures, of; the fall fixed Stars, checareeee 
each of, them to lye in or near the wayof the Genter of the Planet, -arid 
the exa¢t meafure of the apparent Diameter 5 from. the comparing’ of 
fuch Obfervaticns together, we might, certainly know'the true diftance; 
or Parallax, of the Planet. And having any one true Parallax of thefe 
Planets, we might very eafily have the other by, theirapparent,Diame> 
ters, which the Tele(copelikewile affords us very. accurately. And thence 
their motions might be much better known, and-their Theories. more,ex- 
actly regulated. And _for this purpofe; I know, inot,any’ one place.more 
convenient for fuchan Obfervation to be made in, then in the Ifland.of 
St. Helena, upon the Coatt of Africk,, which lyes. about fixteen degrees 
tothe Southwards of the Line,, and, isvery mears,according to the lateft 
Geographical Maps, in. the fame Meridian with Lendom; for-though 
they may not perhaps lye exactly in the fame, yet.their Obfervations, 
being ordered according to what 1 hall anon fhew, it will not be diffi- 
cult to find the truediftance of the Planet. But were they both under 
- the fame Meridian; it would be muchbetter. ie 2 A tg HEE 
“And becaufe Obfervations may. be much. eafier, and more accurately, 
made with good Telefcopes, then with.any, other Inftruments, it wall.not, 
Ifuppofe, feem impertinent to explain a. little what, wayes| judges 
fit and. convenient for that particular... Such: therefore as fhall be 
ao 
sts 
Obfervators for this purpofe, fhould be furnifhed withthe belt pelghapest 
that canbehad, the longer the better. and. more,exaét will their Oblet= 
vations be, though.they are. fomewhat the more. diflicultly manag'd. 
 Thefe fhould be fitted with a Rete, or divided Scale, plac’d at fuchaydi- 
{tance within the Eye-glafs,that they may be diftin@ly feen, which thould 
be the meafures of minutes and feconds 3 by this Inftrument_ each Ob- 
 fervator fhould, at certain prefixt times, obferye the Moon;.or other 
Planet, in, or very near, the Meridian 5. and becaufe it may be very, diffi- 
cult to find two convenient {tations that will happen, tobe. jut under the 
fame Meridian, they fhall, each of them, obferve,the 
both for an hour before, and an hour after, it. arrive at the h 
and bya line, or ftroke, amongft the {mall fixed. Stars; they.f 
N: bfery'd the Center of; the Fiat 
out the iy ae each.of them obierv, ter cath 
mov'd in for thofe two hours : Thefe Obfervations each: 
repeat for many dayes together, that both it may happen, that-both of 
way of the Planet 
2a4 
