[ 3 6 9 ] 
fiiort of three English Feet; a much lefs Quantity 
than which would eafily difcover itfelf in the Sha- 
dow, whofe Length, notwithftanding all Difficulties 
arifing from the ‘Penumbra, might certainly be de- 
termined to lefs than half a Foot. 
I fhall juft add to this Remark the Defcription 
given % Pliny of this Gnomon ; who, fpeaking in 
his xxxvi. Book , § XIV. of the Obelisks that were at 
Rome in his Time, adds, in the Beginning of § XV. 
Ei, qui eft in campo , clivus Auguftus addidit mira * 
bilem ufum , ad deprehendendas foils umbras , dierum - 
que ac milium it a magnitudines , Jlrato lapide ad 
magnitudinem obelifci , cui par fieret umbra , brumce 
confeilce die , fexta hora,paulatimque per regulas (qu<e 
funt ex cere inclufa) Jingulis diebus decrefceret , ac rur - 
fus augefceret . From which Defcription I under- 
ftand, that there was laid down, from the Foot of 
the Obelifc Northward, a level Pavement of Stone, 
equal in Breadth to the Breadth of the Obelifc itfelf, 
and equal in Length to its Shadow at Noon upon 
the fhorteft Day ; that is to fay, that its Length was to 
the Height of the Obelifc almoft as 22 are to 10 ; and 
that into this Pavement there were properly let in 
parallel Rulers of Brafs, whofe Diftances from the 
Point, direftly under the Apex of the Obelifc, were 
refpedively equal to the Lengths of the Shadow 
thereof at Noon,, on the feveral Days of the Year ; 
as the fame Lengths decreafed from the fhorteft Day 
to the longeft, and again increafed from the longeft 
Day to the fhorteft. 
After which the Author mentions in a Paftage 
greatly corrupted, and therefore now almoft unintel- 
ligible 5 that one Manillas , or Manlius , had added 
Bbb 2 to 
