"You know," I said, "that there flows through my estate near Casinum[169] a stream which is both deep and clear and fifty-seven feet wide between the masonry embankments, so that it is necessary to use bridges to get from one part of the property to the other. On the upper reach of this stream is situated my Museum[170] and at a distance of 950 feet below is an island formed by the confluence of another stream. Along the bank for this distance is an uncovered walk ten feet broad and between this walk and the field is the location of my aviary enclosed on both sides, right and left, with high masonry walls. The _ornithon_ itself is built in the shape of a writing tablet with a capital on it, the main quadrangle being forty-eight feet wide and seventy-two feet long, the capital semi-circular with a radius of twenty-seven feet. To this a covered walk or portico is joined, as it were across the bottom of the page of the tablet, with passages leading on either side of the _ornithon_ proper which contains the cages, to the upper end of the interior quadrangle [_adjoining the capital_]. This portico is constructed of a series of stone columns between which and the main outside walls are planted dwarf shrubs, a net of hemp being stretched from the top of the walls to the architrave of the portico, and thence down to the stylobate or floor. The exterior spaces thus enclosed are filled with all kinds of birds which are fed through the net, water being provided by a small running stream. On the interior sides of the porticos, and adjoining them at the upper end of the interior quadrangle, are constructed on both sides two narrow oblong basins. Between these basins a path leads to the _tholus_, or rotunda, which is surrounded with two rows of columns, like that in the house of Catulus, except that I have substituted columns for walls. Beyond these columns at the end is a grove of large transplanted trees forming a roof of leaves, but admitting light underneath, as that is entirely cut off by the high walls on the sides. Between the exterior row of columns of the _tholus_, which are of stone, and the interior row, which are of pine, there is a narrow space, five feet in width. The exterior columns are filled in with a transparent net instead of walls, thus permitting the birds to look out upon the grove and the wild birds there but without escaping: the interior columns being filled in with the net of the main aviary. The space between the two rows of columns thus enclosed is equipped with perches for the birds in the form of many rods let into all the columns in ascending array like the degrees of a theatre; and here are enclosed all kinds of birds, but chiefly singing birds, like nightingales and blackbirds, for whom water is conducted by means of a small canal and food is supplied under the net. [_Under the lantern of the tholus is a basin of water: and around this_] a foot and nine inches below the stylobate or pedestal of the interior row