of opinion, that the crossing in the manner proposed, is the easiest, the safest, and the most permanent and durable; 3d, Because this is the unanimous opinion of the Commissioners, and of the whole corps of engineers engaged on the works, and in this opinion they are joined by several engineers of eminence, not connected with the operations, CROTON AQ.UEDUCT. 4th, Because the high arches will cost half a million of dollars more than the syphons, and will also require two or three years more time to erect them. 5th, Because the Commissioners are advised, by counsel learned in the law, that the Act of the Legislature authorises the passage of the water by the plan proposed by them. 6th, Because, notwithstanding these considerations, the question was submitted by the Commissioners to the Common Council, and their instructions requested, which they promised to follow, whether such instructions should be in favor of the high arches or of the syphon ; but they have declined instructing them on the subject, or assuming the responsibility of changing the plan of the Commissioners ; and now, believing it to be our duty to carry into effect that plan which shall require the least expenditure, and which may be completed in the shortest time, while it takes nothing from the permanence and usefulness of the object, we have adopted the plan by syphons. With these impres- sions, and in a firm belief in their correctness, it would be the height of impropriety in the Commissioners, under the circumstances of the case, to change or abandon the plan they have adopted ; and they will therefore proceed in its execution, unless restrained by due course of law." The summer of 1838 was one of unusual drought ; which, while favorable to the work in hand, especially in the masonry, afforded an opportunity of comparing the flow of the Croton with that of ordinary seasons. Accordingly, on the 16th August, Horatio Allen, Esq., principal assistant engineer, guaged the stream at two different stations — the one gave as the result 26,386,560 gallons, running in 24 hours, the second, 28,738,000, averaging 27,584,780 gallons, or nearly three times the supply requisite for the population of the city at that period. On 5th September, 1833, Major Douglas guaged the river, and found 51,522,486 gal- lons running ; and on 26th of the same month, Mr. Stein found 50,074,044 gallons. These were considered as fair averages of what may be depended on — though at times the Croton rolls to the Hudson several hundred million gallons daily. But over and above the running supply, the Croton lake created by the dam, is estimated to contain 100,000,000 gallons for each foot in depth from the surface, and this may be drawn down five or six feet, yielding as many hundred million gallons. The receiving reservoir will contain 158 millions of gallons, and the distributing reservoir 19 millions — altogether forming an aggregate surplus, in case of excessive and long continued drought, sufficient for any possible emergency. The work performed during the last six months of the year is thus summarily stated : " 1st. Aqueduct. The whole length of aqueduct, arched and complete, is 59,169 feet 41 162 or eleven and one fifth miles. That completed on the first of July last was about two miles. The increase, in this part of the work, since our last report, is nine and one fifth miles of aqueduct complete. 2d. Side Wall. The length of side wall, ready to receive the arch, exclusive of that already arched, is 1443 feet. 3d. Culverts. There are 79 culverts completed and in use. Their aggregate length is 5476 feet. The number completed at our last report was twenty-two, and their length 1825. Increase, 57 culverts. The number now partly finished is ten, and their length in feet 652. The number partly finished at our last report was seven; length 578. Increase, 3 culverts in progress. Tunnels. The number of tunnels excavated throughout is three. Their aggregate length 667 feet. There are, besides, seven tunnels partly finished, measuring 1187 feet of excavation; making .an aggregate of tunnelling of 1854 feet. The number complete at our last report was three, arid the length 670 feet, together with five partly finished, measuring 610 feet in length, making a total of 1280 feet. Increase in this description of the work 574 feet of tunnelling. Foundation and Protection Wall. The foundation wall laid is 58,439 cubic yards, and of protection wall 36,590 cubic yards; making a total of 95,029 cubic yards. The quantity of foundation wall, laid at our last report, was 28,000 cubic yards, and of protection wall 13,160; making a total of 41,160 cubic yards.. • Increase since our report in July last, 53,869 cubic yards. This is a