Barnum's Museum-Letter from its Proprietor.

We have received the following communication from Mr. P.T.Barnum regarding the reopening of his Museum in its new quarters.  He Say:

To the Editor of The N.Y. Tribune.

Sir: the public, generally, I have reason to believe, regarded the destruction of the American Museum as a national loss, and I have the assurance that they are interested in my efforts to restore an institution to which families, strangers, and the community at large, resorted for instruction, blended with healthful amusement.  I am happy to announce that, during the last fifty days, neither myself nor my agents have been idle.  More than a hundred carpenters, masons, painters and decorators have been busily engaged in transforming two large buildings (in Broadway above the St. Nicholas Hotel) into a spacious and beautiful Museum.  The building is twice the depth of the former, extending to Mercer-st. in less than five minutes.

Already five spacious saloons contain a 100,000 curiosities, consisting of rare quadrupeds, birds, fish, shells, minerals, historical relics, &c., and my agents in nearly every part of the world are doing all that energy and a liberal outlay can accomplish toward making this the fines collection of curiosities on the globe.

The grand aquaria with their beautiful fish, a true picture of life in the waters, afford a new pleasure to the most refined classes, while the varied cosmorama, exhibiting scenes from every portion of the globe, imparts agreeable and valuable information to old and young.

More than fifty thousand dollars have already been expended on this collection and in producing a superbly-finished lecture-room with splendid decorations and scenery.  A superior dramatic company is engaged, and a rapid succession of moral dramas, magnificent spectacles and occasional equestrian performances will be produced for the gratification of the public, who have always generously acknowledged my efforts to please.

I have learned by happy experience that he who gives the people the best and most that is possible for their money, may rely upon their constant and increasing patronage, and I shall never fail to be governed by this practical lesson.

I have only to add to this outline that the new Museum will be opened on Monday, Sept. 4, and that I shall immediately afterward proceed to Europe to enlarge and expedite important purchases and arrangements now in progress by my agents.

              Yours truly,                                 P. T. Barnum.

   New-York, Aug. 30, 1865