The question is one of great importance, and surrounded with embarrassing difficulties, which in some respects are of a nature that do not admit of exact, or even hardly approximate, computation. In relation to the time required for the completion, I think five years as little, as should be calculated for the bridge while the tunnel, if successful in putting ;

down the coffer dam, may be completed in four years. It is not probable that either plan can be executed as early as other parts of the aqueduct and it will be proper to lay ;

down a temporary pipe, which may be sufficient for the introduction of the water as for ;

the want of suitable fixtures, some time will probably elapse, after its first introduction, before it will get into general use in the city. A twenty-two inch main may be laid down and protected for $30,000, and when the work is completed may be taken up and used to supply the city mains, by which the extra expense will not be much, if any, over $20,000. In making up an opinion which of the two plans should be adopted, I have felt the question to be one involving great responsibility. The high bridge I have heretofore endeavored to avoid, as a work of great expense, and attended with much difficulty in its execution. From the considerations before detailed, I have however come to the conclusion, that under the modificationnow presented, it is better to adopt it, than the plan of carrying the aqueduct by a tunnel under the river. Could I have the same confidence in the estimate for the tunnel that I have in the bridge, I should have less in coming to this conclusion than I now feel for although the tunnel estimate includes all that appears ;