Why does the Sanitary Commission need so much money? Because the present machinery of the Commission, supported by the Central Treasury cannot be kept in motion without large expenditures; and large as the cost is, the results for good are almost infinitely larger. The Sanitary distributes the supplies sent, embraces Sanitary Inspection by medical men of general hospitals, Sanitary Inspection by medical men of camps and field hospitals, Special Relief with all its agencies and in all its various departments, and the Hospital Directory with its register and its 500,000 names. Every dollar expended meets some real want, or helps to save a life. Do the people wish this agency in behalf of the soldiers in tent, hospital, and on the battle field--at the East--West--South, to cease? or is it their will to continue it in its largeness of plan, its scientific exactness, its ability to do all that the friends at home would themselves desire to do for our soldiers? Our generous and loyal people have given their entire confidence to the Sanitary Commission--they have decided that it shall not die for lack of material aid, estimating beyond all money and all price the lives and health of the brave men now in the field for the defence of the country, and grateful that they may repose in the certitude that every cent contributed will be used in the surest manner to effect the results required. To aid in sustaining this beneficent institution, New York is about to inaugurate a great Metropolitan Fair. She asks in the sacred name of freedom and humanity that her children come together with the works of their hands, the results of their enterprise, the achievements of their talents, the bloom of their genius, to do her honor in a Great Exhibition of Art, Industry, Commerce, all devoted to the cause of human progress. She begs of her children to do the work which is given them to do, with a spirit of love and patriotism, remembering no private griefs, no unworthy animosities; remembering only the bleeding sons of the Republic, who threw themselves, in their youth and strength, into the yawning gulf which opened before them, hoping that, propitiated by such a sacrifice, it might close again--willing to die, or live maimed and suffering, that a happy, peaceful and united people might again possess the fairest land which God has given to mankind. Chicago, Cincinnati, and Boston have already done nobly in this direction, and New York should contribute in proportion to her means and advantages. The Atlantic seaboard should make great exertions, seeing that more than one half of the money received by the Commission has been contributed from the shores of the Pacific--California having sent more than five hundred and twenty-five thousand dollars.