70 



about eighteen minutes, when the columns were at their proper depth. 

 So long as the pumping continued they were loose and easily moved 

 around in the sand; but within three minutes after the pump stopped 

 they were almost as firm as if set in stone, the sand having settled so 

 compactly around them. The method was a complete success, and I 

 see no reason why columns could not be sunk to almost any depth by 

 the same process. Upon the tops of the columns were placed wrought 

 iron beams carrying the floor and pumps. Stone steps were built spi- 

 rally into the wall of the well to enable visitors to reach the pump plat- 

 form. A floor has been laid over the well leaving a circular opening 

 twenty feet in diameter. The floor is supported on two isometrical 

 trusses. The entrance to the well is through the Boiler House and a 

 side opening in the wall of the well. 



FORCE MAIN". 



The Force Main leading from the Pump to the Reservoir is a cast 

 iron pipe twelve inches in interior diameter. Its length is to be four hun- 

 dred and sixty-five feet, and the elevation of the point at which it de- 

 livers the water into the Reservoir is one hundred and sixty feet above 

 the level of the water in the well, and one hundred and seventy-three 

 feet above tide level. The main was made with bell and spigot joints, 

 the bells being five inches deep, and the lead joints were made only 

 three and one-fourth inches deep, the balance of the space being filled 

 by a hempen gasket. 



The force main delivers the water into the Reservoir just above its 

 high-water line. The object in pumping to this height rather than into 

 the bottom of the Reservoir is to insure a uniform pressure on the pumps. 

 In the force main near the pump is placed a check-valve. This is a 

 self-acting arrangement by which the pressure of the water in the main 

 is prevented from acting on the pumps while they are not in motion, 

 and consists of an inclined partition across an enlargement of the pipe, 

 with valves on the upper side, which are opened as the water is forced 

 through them from the pumps, and which are closed by the pressure of 

 the water in the pipe above them. At a distance of eighty-three feet 

 from the well, and at an elevation of about sixty-one feet above the 

 surface of the water in the well, there is a branch connecting with a 

 fifteen inch vitrified pipe which leads to the lake near the proposed site 

 of the Refectory. This branch will be used when it is required simply 

 to fill the lake. 



At a distance of one hundred and fifty-four feet from the well, and at 

 an elevation of ninety feet above the water in the well, is another 



