In 1694, the Cardinal Orsini, having proposed to the Papal government to bring water from the Lake Bracciano (anciently Alsietinus) to Rome, in the ancient channel of the Aqua Alsietina, the architect, Paglia, examined the levels, and stated that a sufficient quantity of water could be obtained and directed into the channel as projected by the Cardinal.Permission was accordingly given to the Orsini family to commence operations, on condition of furnishing about a third part of the water for the supply of one of the new public fountains, and dividing with the apostolic chamber, th revenue which would arise from the disposal of the remainder.

PRELIMINARY ESSAY. 47

The cavalier Bernini, having the direction of the new fountain before St. Peter's and wishing by means which appeared to him less exceptionable than those to ascertain,

employed by Abbe Paglia, whether the quantity which had been stated, as being at his disposal, could be obtained or depended upon, committed the examination of the levels to his brother, who gave his opinion against the practicability of obtaining that quantity which the Cardinal anticipated, on account of the small declivity of the channel of the aqueduct, and the variations in the levels of the lake itself. The Pope having directed new experiments and observations to be made, it was found that although the level of the lake was about one and a half palms above the surface of the ancient reservoir which fed the aqueduct, that this additional head was insufficient to produce the velocity to furnish the supply which was considered to be desirable. To obtain this velocity, a weir or dam was erected across the mouth of the lake to preserve its waters at the proper height, and the usual means of regulating the head, and disposing of the superfluous water by sluices was resorted to.