THE Nilometer is a graduated upright pillar, placed in a well within a walled inclosure, built on the island, into which the waters of the Nile are admitted by concealed channels. The amount of tax levied upon the land is guided by the fertility which is expected to be consequent upon the maximum of the rise which the pillar indicates; but it is said that the height of the Nile is as often suited by the government to the state of the exchequer, as the tax is guided by the rise of the Nile.

That the building is of comparatively modern date, is shown by the arabesque ornaments on the gate by which the water passes, and by the Kufic inscriptions on the walls, to be not more than nine hundred years old; but it is highly probable that its site was appropriated to the same purpose at a remoter period. The large building which now incloses the whole is used as a powder-magazine, and all access is denied to strangers. Mr. Roberts got access to it by climbing over the wall, and made a hurried sketch, but at the risk of being drowned in the well of the Nilometer, or shot by the sentinel.  

Roberts's Journal