Hence I walked to Castel Gandolfo, and down to the shores of the lake, which must be near 300 feet below the palace of the popes. Some fishermen were drawing their nets, but all they had caught consisted of two or three moderate sized tench, and a quantity of small fry. My principal object here was of course to see the celebrated _Emissario_, which as you know is an artificial subterraneous channel, of considerable length, made by the Romans to discharge the waters of the lake, and it is still the only passage they have; but the story of its formation is a very strange one. During the siege of Veii, the waters of the lake rose in dry weather to a very extraordinary elevation, so that the Romans were afraid it would overflow; terrified by the prodigy, they sent ambassadors to Delphi to learn what was to be done, and the answer enjoined them to let out the waters, but to take care that they did not flow into the sea. Now the lake is a complete crater, without any continued valley by which it could ever have found a natural outlet, and to have overflowed the edges of the basin would have required an elevation, above the present level, of I suppose 150 feet.[10] A few trifling springs on the banks, and probably some underwater, form its permanent supplies, and the country which drains into it, is of such small extent, that I do not believe six inches of rain would raise it thirty feet from its present level, and not a fourth part of that, if the water stood nearly up to the top of its banks. Perhaps this wonderful rise proceeded from some volcanic discharge; yet the danger does not seem to have been very pressing, since the Romans had time to send to Greece for instructions. The direction of the existing channel is nearly in a line towards the shore, but the natural direction of the hollows which receive it, conduct it towards the Tiber, into which it at present flows, yet it may have been dispersed, and perhaps in summer lost before it arrived there. The whole looks very much like a scheme to procure an irrigation for some lands whose dry soil produced but little. If the lake was to be lowered 150 feet, the tapping it would be both difficult and dangerous; but if it was only necessary to lower it 15 or 20, the execution would not require any great degree of contrivance; and the soil, which is a soft rock, yielding probably in its hardest parts to the pick-axe, and yet everywhere firm enough to maintain itself, facilitated the enterprize. It is however a wonderful work; above a mile and a half in length, and 250 feet from the surface. The front of it was faced with stones, leaving a rectangular opening, covered with a large square block of peperino, which is the material of the rest of the work, and this stone being found near Albano, is likely to have been more exclusively in use here than at Rome. This is probably the original work, but in front, there is now a vault of no great extent, of the same material, but not