The Shelves · Mathematics (incl. astronomy)

On the Measurement of the Earth

Περὶ τῆς ἀναμετρήσεως τῆς γῆς

Known · Attestedin Alexandria?Conjecturedvery likely classLegend · Told storya told story on its tag

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I · The entry, in his form

In the table of Mathematics (incl. astronomy)

Conjecturedvery likely class

Eratosthenes of Cyrene

c. 276–194 BCE. The Suda says Ptolemy III summoned him from Athens. P.Oxy.

On the Measurement of the Earth

Περὶ τῆς ἀναμετρήσεως τῆς γῆς

Opening words not preserved.

Length: not counted

Above, his entry form, filled from what we know. Below, ours.

II · Does it survive? Where to read it

Lost

Known from Cleomedes' summary and later citations.

Was it in Alexandria?

Known · Attested

Written in Alexandria.

In the cupboard: written at Alexandria by a scholar or court writer a source places there.

Read it today

III · In the show

The show has not yet spoken of this work.

IV · Sources and the living entry

Ancient references (3)
  • Cleomedes, Caelestia 1.7
  • Pliny, Natural History 2.247
  • Strabo 17.1.48
Modern scholarship (3)
  • A. C. Bowen and R. B. Todd, Cleomedes' Lectures on Astronomy (Berkeley: University of California Press, 2004).
  • D. W. Roller, Eratosthenes' Geography (Princeton: Princeton University Press, 2010)
  • K. Geus, Eratosthenes von Kyrene: Studien zur hellenistischen Kultur- und Wissenschaftsgeschichte (Munich: C. H. Beck, 2002)

Entry checked 31 Oct 2026 · no corrections · Suggest a correction ›

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Read what is told

The back of the tag: a story told of this work, in its teller's voice.

Legend: told story

The well at Syene

Modern retellings tell that Eratosthenes heard of a well at Syene where the noon sun shone straight to the bottom on the longest day, and measured the Earth from it.

Told by Modern retellings, modern retellings, more than two thousand years later

What the evidence supports

Cleomedes' summary of the measurement uses the sun overhead at Syene and a sundial's shadow at Alexandria, one-fiftieth of a circle; it has no well. Strabo mentions a well at Syene that marked the solstice, but not in connection with Eratosthenes.

Sources (2)
  • Cleomedes, Caelestia 1.7
  • Strabo, Geography 17.1.48
The Hall of Told Stories

Beside it in the cupboard