After a most interesting and agreeable visit, we returned by water to Boston. The sea was blue as a plain of sparkling sapphire--quite Mediterraneanic! Nahant is certainly a delightful place of summer residence, though it wants shade; trees in general most positively refuse to grow there, and there are but a few, which are taken as much care of as if they were the most precious exotics; but Nahant and they do not agree. They have quite a pouting sulky look; and it is almost as sad to look at them as it is to see the _girdled_ trees, which look like skeletons of malefactors bleaching in the wind. At dessert, at Mr. Prescott's, there was a huge magnificent water-melon, that almost might have taken the place of the Cochituate Pond, and supplied Boston with the crystal element for a day. In returning through the harbor of Boston from Nahant, we were full of admiration of its scenery: the many lovely islands with which it is beautifully studded, and the superb view of Boston itself, so nobly surmounted by its crown-like State House, enchanted us. MR. AND MRS. J. GRINNELL.--NEW BEDFORD AND NAUSHON. Since I wrote this, we have had a very agreeable little tour. We have received, through Mrs. W----, a kind invitation from Mr. and Mrs. J. Grinnell to visit them at New Bedford. That town is called "the City of Palaces," from the beautiful buildings it contains: it is also the great whaling metropolis of the North. It is about fifty-six miles from hence. The Americans give their cities most poetical and significant designations, and sometimes one town will have a variety of these. For instance, this, I believe, is not only called the Granite City, but the Trimountain City. Philadelphia is the city of Brotherly Love, or the Iron City. Buffalo, the Queen City of the Lakes; New Haven, the City of Elms, &c. I think the American imagination is more florid than ours. I am afraid matter-of-fact John Bull, if he attempted such a fanciful classification, would make sad work of it. Perhaps we should have Birmingham, the City of Buttons or Warming-pans; Nottingham, the City of Stockings; Sheffield, the City of Knives and Forks, and so forth. Mr. and Mrs. Willis, and Mr. Willis's musical brother, were at Mr. and Mrs. J. Grinnell's beautiful mansion. We paid a visit to an immense whale-ship that is in the course of busy preparation for her voyage--to the South Seas, I believe. The whale-fishery is very extensively carried on at New Bedford. The population is about fifteen thousand, almost all engaged directly or indirectly in this trade. There are about two hundred and twenty-nine vessels engaged in the fishery, which is said to be continually increasing.