Page:Philosophical Transactions - Volume 145.djvu/131

Rh Fig. 1. Curve of the Surface of the Nile in 1846.

0⋅50 metre=18,685 English inches. 7⋅20 metres=23 feet.

From the increased fertility of the land by the overflowing of their river, the earliest inhabitants of Egypt must have been led to watch the rise and fail of the water with anxious care. At an early period in the history of the country they contrived an instrument to measure its diurnal changes, a Nilometer, which was erected on the island of Elephantine near Assouan. That instrument is now only an object of interest to the antiquarian, as a ruin is all that is left of it; but it was in a state of considerable preservation a little more than fifty years ago when visited by the French engineers. I describe it now, as it then existed, because special reference will be made hereafter to this ancient standard of the Nile's annual increase. It is near the south end of the island, and is described by from personal observation, he having twice visited the spot.

The French engineers have given the following description of it as they found it. It was in a building constructed of regular horizontal layers of sandstone, having two flights of steps, at right angles to each other. One of the walls of the staircase was marked with a vertical groove, crossed by horizontal lines, at regular distances, each of these divisions being a cubit. Three of these divisions were marked with the Greek numerical letters, the highest being KΔ, or 24; the second KΓ, or 23; the fifth K, or 20. The engineers assumed that at the time this Nilometer was constructed, the number 24 marked the greatest rise of the Nile then known. M. and his companions made an exact measurement of the cubits from 24 to 18, and the result gave 527 millimetres for each cubit, =20⋅75 English inches. Sir, from personal observation and examination of the different