142 INTRODUCTION. 



provision for street arches is composed of a continuous wall of masonry, carried 

 up on a bevel of one-tvvrelfth its rise to the grade line of the aqueduct, vi^here it 

 is thirty feet wide. The outside or face of this wall, for one foot in breadth, is 

 laid in hydraulic mortar, and the remainder is dry masonry, consisting of courses 

 of large stone, with the interstices thoi'oughly filled with small broken stones. 



The receiving reservoir is formed with earth banks, the interior having 

 regular rubble walls, and the outside is protected by a stone wall laid up on a 

 slope of one horizontal to three vertical ; the face laid in cement mortar, and the 

 inside dry. The inside is protected by a dry slope wall laid on the face of the 

 embankment, which slopes one and one-half horizontal to one vertical. The em- 

 bankments are raised four feet above the top water line, and vary in width from 

 eighteen to twenty-one feet. Vaults or brick archways are constructed, in which 

 iron pipes are laid, so arranged that the pipes from the northern division of the 

 reservoir connect with those of the southern division, and thence pass off to the 

 distributing reservoir, and to supply the adjacent districts. The vault on the 

 eastern side is 540 feet long and is 16 feet span ; that on the western side is 400 

 feet long and 8 feet span. The pipes are all provided with stop-cocks, and so 

 arranged that they can receive water from either division, except one pipe from 

 each division leading to the distributing reservoir. A pipe is put through the 

 division bank with a stop-cock, to allow the water, or not, to pass from one divi- 

 sion into the other. The aqueduct insersects the reservoir at right angles with 

 its westerly line, and 252 feet south of the northwesterly corner. At this point 

 a gate chamber is constructed, with one set of gates to pass the water into the 

 northern division, and another set to pass it into a continued conduit of masonry 

 constructed within the embankment of the reservoir, to the angle of the south- 

 ern division, which the water there enters by a brick sluice. This arrangement 

 gives the power of directing the water into either division, or both, at the same 

 time. A waste-weir is constructed in the division bank. It has not been deemed 

 necessary to complete the excavation of this reservoir. It has at pi-esent a capa- 

 city for 150,000,000 imperial gallons. 



