Major Gunther to-day sent tbe following letter to Maj. Gcu. Saniord : MayorTs Office, ]Sew York, J;:ly 11. To Maj. Gen. Sanford, Sir : - In these times of general and local peril, enlightenod selfinterest ia emphatically the synonymof patriotism. The paiamount cluty of all llnose in authority, whether civil or military, is to careiully guard the lives and property of their own citizens. Here in New York, the great centre oi commerce and weiilth,it is a consideration oí the first importance, not only to ourselves hut to thb general public vveal, that we should not, by any action of otir oin, place tbese great interests in jeopardy by withdrawing our legitímate protection. This protection, in case of riot or popular outbreak, is especially re posed in our organized sity regiments I entertain gravo apprehensions that their wilhdnnval from the city, when the depreciation of our currency is bearing heavily on the maas oi our popularon, might tempt the lawless and evil disposed to avail therriBtlves of what would seem to theni a favorable opportuiiity tor arson and plunder. Isi such dn event, which 1 regret to say, in my judgment, may not be coosidered improbable, 1 iear our excellent and powerful pólice would prove inadequate to our protection in the absence of the military. I therefore most earnestly protest ngainst any material reduction at this period, of our organized and uniforuaed military force, espeeially when imple snpplies of troops can be furnished to meet any emergency, troon points where no danger can be apprehendcd of the character above alluded to, and to which the city of New York is so peculiarly esposed. I have the honor, to be, very respectfully, youi obcdient servant. [Signed,] C. GODFREY GUNTHER. New York, July 12. Thefollowing is the reply of Major General Sanford to tho letter of Mayor Gunther : Ist División N. Y. State National ) Goard, New Yokk, July 12. y Hon. 0. G. Gunther, Mayor ot the city oí New York. Sir: Although I can not concur in your definition of patriotism, I fully agroe with you in the necessity ofretain. ing au organized and discipliued force in our city sufficieutly strong to suppress any attempt of the Iawless and evil diaposedmembersof the coiumunity to renow the scènes of arson and muider which disgraced our city last summer during the absence of. our city regiments In answer to the present cali of the President on the Governor of tbe St.te, only 3,500 men have been detaiied from this División as our quota of the 10,000 roquircd, and after this detachment is withdrawD, I ghall retain 12 of the disciplin ed regiments of the Ist División n the city, ready, willing, and abuudantly able to put down promptly any demoustration against the peace and good oiderof the community. I rogret tliat after the explanation to you yesterday in person, you should have deeiued it necessary to publish your letter, and I hope, therci'oro, you will have no objection to the publication of this auswer, to allay any fears which you may have exited. I am, very respectfully, Your ob't servant, [Signed] C. W. SANFORD. The Richmond Sentinel claims that the rebel government gathered tliirtyeight thousand email arms on the biutlt'ground ol the WildernesB.