GEOGRAPHY, 
fllliis or gnomon creeled vipon a hodzontal plane, by 
which they were enabled to meaCure the lengtli or diort- 
jiel's of tlie fliadow, in proportion to the height of the 
■ililiis. ' It is difficult to fay which of thefe two nations 
are beft entitled to the credit of the invention. Hero¬ 
dotus, whofe geographical notices are the firli that af- 
funicd a connected and confilfent form, tells us, that the 
Greeks firfl; learned the pole, the gnomon, and the 
twelve divifions of the day, from the Babylonians. But’ 
in anfwer to this alfertion it may be obferved, that the 
merit of this invention of the gnomon in Greece, is 
-afcribed by Pliny and Diogenes Laertius, to the altro- 
■fiomical fchool of Miletus, and particularly to Anaxi¬ 
mander and Anaximenes, the difciples of Thales; and 
,there is rcafon to believe that this method of obferva- 
Tion was well known to Thales himfelf. For though 
the aClual eredfion of a gnomon was an honour referved 
for one of his immediate fucceffors, who placed at La¬ 
cedaemon the firft fun-dial upon that conftrudlion that 
was feen in Greece ; yet it may be prefumed at the fame 
time, thatTluiles, who had travelled into Egypt, where 
lie learned both his geometry and aflronomy, might 
bring from thence the idea alfo and principle of this in- 
•dlrument of obfervation ; for Diogenes Laertius particu¬ 
larly mentions, that he was the firft who found out the 
pafiage of tlie fun from tropic to tropic. By what in- 
flrumcnt, then, could this be determined, unlefs by the 
gnomon ? For the adrolab and the armiliary circles are 
generally believed to have been invented by fome of the 
later Greek alironomers who flouriffied under the Ptole¬ 
mies, fuch as 'I'imocharis, Ariftillus, or Eratofthenes. 
Thales is likewife faid to have been the author of 
two books, one on the tropic, and one on the equinox, 
the exatf times of which he probably deter ained by the 
ffiadows of the gnomon ; and by this he was naturally 
led to another of his difeoveries, which was the divifion 
of the year into its four feafons, which was a confequence 
of his finding the particular days when the fun appeared 
to be in the tropics and in the equinox. His divifion of 
the year into 365 days, was undoubtedly brought by 
him from Egypt, as it is univerfally allowed to have 
been an Egyptian difeovery prior to his time, being af- 
cribed to the fecond Mercury, fir-named Trifmegilhis, 
■who is fuppoled to have lived about fifty years after the 
Exodus, according to Eufebius. And Pliny tells us ex- 
prelsly, that the difeovery of this length of the year by 
the addition of the five days and a quarter to the 360, 
was made by obferving when the ffiadow returned to its 
marks ; which is a clear proof that it was done by the 
ufe of a gnomon. And th.at the taking the lengths of 
the fhadow, by way of calculation, tvas ai: idea familiar 
to Thales, appears.from his firft inventing the method 
of determining the height of the pyramids by their 
fliadow at that exadl inlfant of time in the day when 
the lhadow of a man is found to be equal to his lieight. 
It does not therefore feem to be an improbalile lup- 
pofition, that tliis method of obferving by the gnomon 
was originally imported from Egypt, where it was 
known long before any dawn of the Greek learning; for 
if has been the opinion of I'everal eminent writers, that 
their pyramids and obeli Acs, which to common travel¬ 
lers appeared to be buildings merely of ornament and 
jnagnificence, were really fun-dials upon an immenfe 
fcale, by which the variation of the length of the fnadow 
in proportion to its height could be taken with a greater 
degree of accuracy. And to confirm this opinion, it 
was found upon examination by M. de Cliazelles in 
169.;, that the two Tides, both of the larger and fmaller 
pyramids, were placed exadtly north and fouth, fo as to 
be true meridian lines even at this day, and the other 
two fides Hood eafi: and well; which is a clear proof, that 
even in thofe remote ages in which they were built, they 
-were io contrived by the Egyptians to (land in the di- 
reflion of the four cardinal points of the heavens, for 
VoL. VIJI. No, 507. 
^41 
the pnfpofes of their agronomical obfervations. — See 
the article Egypt, vol. vi. p. 360-361. 
From the days of Thales and his immediate fucceffors, 
who flourilhed in the fixth century before Cluifi, there 
feems to have been little done towards the folid im- 
provement of geography for two Imndred years, till the 
efiabliffiment of the famous aftronomical fchool of Alex¬ 
andria. For we have fcarcely any fragments remaining 
of the fchool of Pythagoras ; though at the fiime time it 
miifi: be owned, that their having known tlie true'fy Hem 
of tlie world, by placing the fun in the centre, and giving 
the earth both the diurnal and annual revolutions, are 
proofs that their knowledge of this mnft have been 
eflabliflied by clear and accurate obfervations. There 
is however an agronomical obfervation mentioned during 
this period, and it is indeed the firft Greek one that 
{lands on record, and is preferved to us by Ptolemy, 
which is that of Meton and Euflemon, who obferved 
the fummer folflice at Athens, during the archonihip 
of Apfeudes, upon the 2iff of the Egyptian month Pha- 
menotii, in the morning, being the 27th of June, 432 
years before Chrilt. This obfervation was made with a 
view of determining the beginning of their cycle of XIX 
years, which commenced upon the new moon of the i^th 
of July immediately fucceeding (being exaftly eighteeit 
days after the folflice), and fell, according to Diodorus, 
upon the 13th of the Athenian month Scirophorion. 
This folftitial obfervation mufl: have given Meton and 
Euttemonan opportunity of determining the latitude of* 
Athens at the fame time, had they but known thefimple 
manner of drawing the conclufion ; for as the length oij 
the fliadow of the gnomon was narrowly watched at tlie- 
crifis of the folflice, the proportion of that to the height, 
of the gnomon was eafily known, by which the angle of 
the fun’s altitude was given. And though the fun’s* 
greatefl declination was then very inaccurately known, 
being by Ibme fuppofed to be 24°, and by others 23* 
51', which is only found at prefeiit to be 23° 28' 10"', 
yet flill the latitude of Athens might have been deduced 
within the limitations of this error; making at the lame¬ 
time allowances for the grofs manner in which altitudes* 
were determined without proper inftruments, and witiu 
out the folutions of trigonometry, which appears to hav? 
been unknown till the age of Hipparchus, by whom it 
was firli introduced. 
It would feem that Timocharis and Ariflillus, wild 
began to obferve 295 years before Chrifl, were the firft' 
who introduced the manner of determining the pofitions 
of the liars according to their longitudes and latitudes 
taken with refpect to the equator. This we know front- 
Ptolemy, who has preferved many of theirobfervation-s in 
his Alniagefl; one in particular is well known, and it- 
gave rife to the difeovery of the precellioii of the equi» 
noxes ; it was that of the Spica in Virgo, which Ti- 
niocharis found to be 8° welt from tiie auUiimial 
cquiiiodtial point, and likewife that it was one degree 
and two fifths to the north of the equator; both of wiiicii 
were found to be different by Hipparcli'us; fo that this 
bright liar had Ihifted its place wirli regard to thefe two 
particulars in that interval of time elapled betwixt thefe 
two obfervations; for hi one cafe he only found it to be 
6° welt from the autumnal equiiiodlial point ; and iiv 
the other, that it was three-fifths of a degree, or 36', to 
the north of the equator; but it was found both by 
Timocharis and Hipparchus to have remained nearly at 
the dillaiice of two degrees to the foutli of the middle 
of file zodiac or ecliptic. From which it naturally ap¬ 
peared reafonable for Hipparchus to fuppole that the 
fixed liars had a How motion round the poles of tlie zodiac: 
“ But, as Ptolemy tells us, that though inclined to this 
opinion, yet Hipparchus lays of himl'elf, that he hefitated 
in his own mind upon the decifion of the quellion, be- 
caufe the obfervations of limocliaris were not to bq 
coiifidentJy depended upon, as beinfj made in a rough 
4 b planner 4' 
