Charles H. Haswell, U. S. Navy, Engineer and Surveyor of the New York Board of Underwriters, has addressed a very sensible and interesting letter to the President, W. R. Jones, of said Board. He asserts that the reprehensible practice of covering newly paved cobble stone with sand some inches deep, and allowing it to remain to be carried down the sewers and into the docks by rains, is proving exceedingly injurious to the free navigation of the harbor. Were it not for the dredging machines continually in operation in our docks to remove the dirt carried down the sewers they would soon be filled up. The expense of dredging is enormous, while the manner in which it is conducted is more like the work of insane persons than men pretending to common sense. What do our readers think is done with the dirt excavated from our docks by the dredging machines 1 " Taken and wheeled up on dry land to fill up pools behind banks, 'c., every one will say." No such thing, that would be too sensible a method for our lazy, unthinking gothamites. It is taken from our docks and dumped out into the bay " transferred from the slips to the channels of the rivers which bound our city." It is not carried out to the ocean ; the tides roll it backwards and forwards, and some of it comes back to the very docks from which it was originally taken. Is not this a wise system for the sharp men of New York to be pursuing With the increase of our city, if the. same system continues for 30 years longer, the channels to our city will be shoaled up, and New York will become an exclusive resort for oyster boats and such like craft, instead of being as it is now, one of the finest and deepest harbors in the world. Mr. Haswell recommends that our streets should be kept clean, and that a new system of contracting for the removal of filth should be adopted. "The free navigation of our hay is involved in the cleanliness of our streets. This is what he asserts ; we have no objection to the plan he recommends for keeping our streets clean, we like it, but we have so'tnething to say which he has overlooked. There is no necessity for covering newly paved streets with sand and allowing it to remain for some time, under the pretence that it is necessary. The covering UJ>of the newly laid stones with sand is to hide bad work, and put money into the pockets of the paving contractors. We have seen plenty of street paving in our lifetime, but never have we seen work doe so wretchedly as in New York City. The stones should be laid down snug and rammed hard at first, and then all the loose sand swept off. We shall be glad when all our streets are laid with the Russ * pavement, no loose sand is left after it. The cobble stone pavers will then discover that Othello's occupation is gone, and it was principally owing to their inefficient, unscrupulous, and miserable methods