142 INTRODUCTION. 
provision for street arches is composed of a continuous wall of masonry, carried 
up on a bevel of one-twelfth its rise to the grade line of the aqueduct, where 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 thoroughly 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 present a capa- 
city for 150,000,000 imperial gallons. 
