I take this opportunity to write in regard to the American Institute Fair, which was held in the Academy of music in the city of New York from the third to the twenty-third of this month. During the last week the Horticultural Society joined them, and made the exhibition more attractive by an exhibition of fruits, flowers, and house plants. Here as at the New York State Fair, I was gratified to observe that the choicest collections of fruit were largely made up of varieties which have proved hardy in Wisconsin. There were two large and probably choice collections sent from France with their intricate French names; but I think in no way superior to the productions of our own country. The flowers were preserved in dampened sand and were not as well arranged or as well preserved as they should have been. Of house and Green-house plants there was an excellent display of the choicest kinds.

The exhibition of the Institute is more especially for the display of the productions of the mechanical and Fine Arts of the choicest kind and finished in the most attractive manner. They filled the very large Hall of this building and suspended them over hundreds of feet of wall, and from the galleries which viewed by gas light made a most magnificent sight. They seemed to me to be nearly every thing which the interests of Agriculture, Manufacturers, Commerce and the Household could require. Models of Vessels and weapons of War were there; incongruous perhaps Peace men will say; but in my judgement essential, at least, until American Slavery shall be no more.

An unexploded Rebel torpedo was shown with the injunction "hands off." I noticed the command was carefully obeyed. Articles of historical interest were shown; among them a chart which were displayed nearly all the coins and shinplasters which the Rebellion and the retirement of the precious metals have brought forth, to the number of 1282. Also a chart in squares, with a zigzag line drawn across it, showing the fluctuation of gold. I observed that the line ran very high when Conservative Generals were in command, and low when radicals ones were. I think this display a most excellent one for mechanics and scholars; but the machinery is too complicated for me to give to you an intelligent description of. To-morrow I will attend the Fair of this county. If I see anything of Agricultural interest, I will write you.

Yours &c. John C. Wheeler