is considered that this is only one of the parts which make

up the whole. From Clendinning Valley the Aqueduct soon reaches the Receiving Reservoir which is thirty-eight miles from the Croton Dam. This Reservoir occupies an elevated part of the island between 79th and 86th streets and between the 6th and 7th Avenues. It covers seven of the city blocks ; is divided into two divisions, one covering three and the other four of

these blocks. It is 1826 feet long and 836 feet wide from outside to outside of the top of the exterior walls of the embankment, making an area of thirty-five acres. The situation was chosen as one affording the proper elevation : but its formation was such as to present difficulties in the way of making the Reservoir perfectly water-tight the surface, in tracing it from 79th to 86th street, was quite undulating, a portion of it in the southern division of the Reservoir falling below the proposed bottom, and that portion of the surface which was earth, forming only a covering to

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the rock, which over the whole island, presents a singularly broken and uneven formation. In almost every instance of excavation, the rock was found above the proposed bottom of the Reservoir, and the difficulty of preventing leakage along the surface of this rock may easily be conceived ; but considering that measures are taken to prevent such an occurrence, another difficulty is still presented in the formation of the rock : the veins and fissures which are frequent