It has been officially announced that the Crystal Palace will be opened for visitors on the 15th of next month (July.) We hope that nothing will prevent the fulfillment of this announcement, for it operates detrimentally to the character of our country when any such enterprizes are misconducted, so as to disappoint our own people, or those who may come from other countries to visit us. We have said nothing about this affair that has not been dictated with regard to truth. We trust the exhibition will be a good one, and that we shall be able to describe many excellent improvements to our readers, in our usual way, impartially, so as to present accounts of machines and machinery, that may be depended upon lor correctness of description and candor ot opinion. The building is to be much enlarged from the original design. The sole charge of the interior of the building, its division, arrangements, classification and police, has been confided to two officers of the Navy of the United States, Captains S. F. Dupont, and C. H. Davis. These gentlemen have organized their De-, partment as follows :— J. M. B tchelder—Secretary of the Superintendent ; Samuel Webber—Arrangement of Space and Classification; Prof. B. Silliman, Jr.—Mineralogy and Chemistry; H. P. Johnson—Agricultural Implements ; Joseph E. Holmes—Machinery ; Edward Vincent—Textile Fabrics ; J. M. Felix Piatti—Sculpture. The following is the apology offered by the; directors for not opening the Exhibition on the 2nd of May. We consider it an unsatisfactory one :— " The Directors had hoped to open the Exhibition at an earlier period, but the novelty Land intricacy o! the style of construction and the high standard of architectural beauty, which it has been the object of the Association to attain, have produced delay, and it has been impracticable for the Directors, notwithstanding their utmost vigilence, and their most earnest desire, to announce the opening at an earlier day." Capt. Dupont is a member of the Lighthouse Board, and is distinguished for scientific attainments. Capt. Davis has spent some years on the Coast Survey, is also distinguished for scientific attainments, and is now at the head of the Nautical Almanac Bureau.