evacuation of Virgiuia by the rebels.Mr. Short’s Greek Fire.-—The following is stated in a letter to the Boston Fost describing the terrible efficacy of the “Greek Fire” invented by Mr. Short of that city, as a destructive agent io war:During the recent trip of the gun boat Saxon to Ship Islaud, four shells filled with the Greek Fire” were thrown, some upon the enemy’s shore, and others into the air. Those thrown upon the laud (a distance of about three miles) fired a large eanebrakc, whichburnt with great fury, and was still on fire upon the return of the Saxon, five days later. Oue of the shells exploded in the air, jetting a thousand streams of fire in all directions, andi *| illuminating the sky and ocean with a novel and brilliant light. The officer who managed the experiments s^ys that the effects of the§reat sheets of fiam* suddenly bursting out of|arkness was indescribably magnificent. It isno secret in Secessia that thja t*avenging ;fire1 will soon be in their midst. * -