It was not without reason that all the ancients attributed the invention of geometry to the Egyptians. The perpetual encroachments of the Nile and the displacements it occasioned, the facility with which it effaced the boundaries of the fields, and in one summer modified the whole face of a nome, had forced them from early times to measure with the greatest exactitude the ground to which they owed their sustenance. The territory belonging to each town and nome was subjected to repeated surveys made and co-ordinated by the Royal Administration, thus enabling Pharaoh to know the exact area of his estates. The unit of measurement was the arura; that is to say, a square of a hundred cubits, comprising in round numbers twenty-eight ares.* A considerable staff of scribes and surveyors was continually occupied in verifying the old measurements or in making fresh ones, and in recording in the State registers any changes which might have taken place.** Each estate had its boundaries marked out by a line of stelas which frequently bore the name of the tenant at the time, and the date when the landmarks were last fixed.*** * [One “are” equals 100 square metres.--Tr.] ** We learn from the expressions employed in the great inscription of Beni-Hasan (11. 13--58, 131-148) that the cadastral survey had existed from the very earliest times; there are references in it to previous surveys. We find a surveying scene on the tomb of Zosirkerîsonbû at Thebes, under the XVIIIth dynasty. Two persons are measuring a field of wheat by means of a cord; a third notes down the result of their work. *** The great inscription of Beni-Hasan tells us of the stelæ which bounded the principality of the Gazelle on the North and South, and of those in the plain which marked the northern boundary of the nome of the Jackal; we also possess three other stelo which were used by Amenôthes IV. to indicate the extreme limits of his new city of Khûtniaton. In addition to the above stele, we also know of two others belonging to the XIIth dynasty which marked the boundaries of a private estate, and which are reproduced, one on plate 106, the other in the text of _Monuments divers_, p. 30; also the stele of Bûhani under Thûtmosis IV. [Illustration: 125.jpg a boundary stele] Drawn by Faucher-Gudin, from a photograph given by Mariette, Monuments divers, pl. 47 a. The stele marked the boundary of the estate given to a priest of the Theban Amon by Pharaoh Thûtmosis IV. of the XVIIIth dynasty. The original is now in the Museum at Gizeh.