The Commissioners repeat this suggestion without expressing an opinion concerning it, but in referring to the rapid execution of the general work they say " there is hardly a doubt that the whole line from the Croton to the Harlem, will be finished, some years, before the expensive and difficult work over the latter river can be."

Much, however, and of very difficult and expensive construction, remained to be done on the island of New York. Independently of the stupendous works at the Harlem river, scarcely yet commenced, there were the expensive crossings at Manhattanville, and at the Clendening valley, besides the two reservoirs, on all of which, as yet, but little progress had been made. Indeed, so heavy and so costly was the work on the island, that it alone,

176 MEMOIROFTHE extending through only seven miles, was estimated to cost more than three millions of dollars, about two thirds of the original estimates by Major Douglas and Mr. Martineau, for the whole work.

These two engineers, without consultation or co-operation, made separate estimates in 1835. That of Major Douglas, was for $4,786,637 00, that of Mr. Martineau, for $4,225,814 00. The difference arose from the mode of passing the Harlem, which, by Mr. Douglas's plan was on a high bridge, and Mr. Martineau's by inverted syphons, on a low bridge.

With such apparent agreement, the Commissioners were well foun ded in assuming that Jive millionswould certainly accomplish the work, yet the result has proved the estimates in question, to be entirely delusive. This may be explained, without impeaching the sagacity or accuracy of those engineer, by the facts, that they had no actual experience derived from the price at which contracts would be taken that the difference in the cost of land from that which it bore in 1835, and that afterwards placed on it by speculators and interested persons, was beyond calculation and that the prices of work and materials were largely enhanced between 1835 and 1837.