[important news from Petersburg.
Petersburg, July 30.
--The enemy sprung a mine under our works on the Baxter Road, one and a half miles from the city, this morning about 5 o'clock, blowing up a considerable portion of our works, which were occupied by Pegram's battery, of this city, supported by Elliott's South Carolina brigade.
A number of lives w The enemy at once bounded forward driving in our forces and occupying a large portion of our lines.
Mahone being notified of the condition of affairs, harried his own and Wright's brigades to the scene of action.
On their arrival he threw them forward to retake the works temporarily lost.
Bounding forward with a yell, they recaptured a large portion of the line temporarily lost and took forty commissioned officers and four hundred privates, representing four divisions of Burnside's corps.
Among the prisoners were some 20 negroes.
The slaughter of the enemy during the engagement is represented by distinguished officers as the severest of the war for the numbers engaged.
The battle-field is literally strewn with dead negroes.
The firing ceased at 9 o'clock, but it is understood we will renew the attack at 2 o'clock.
Among the casualties are General Elliott, of South Carolina, severely wounded; Colonel Weisiger, commanding Mahone's brigade, slightly; Major Woodhouse, slightly; the gallant Captain Girardy, Mahone's Assistant Adjutant General, slightly.
During the fight the enemy's grape and shrapnel fell thick and fast in the outskirts of the city.
Our loss in prisoners is not believed to equal our captures.
The Yankee prisoners say Grant has been mining three weeks.
[Second Dispatch.]
Petersburg, July 30.
--About two o'clock to-day, everything being arranged, General Mahone threw forward Saunders's Alabama brigade, which charged the enemy in gallant style, recapturing the rest of the breastworks temporarily lost and taking about five hundred prisoners, including one hundred and fifty negroes, thirty five officers and Brigadier-General Bartlett, of the 1st division, 9th corps, besides two stands of colors and four pieces of artillery lost by us this morning.
Over six hundred of the enemy's dead are in our trenches.
Mahone's and Wright's brigades, besides prisoners captured this morning, took ten stands of colors.
One lines are now identical as before the fight this morning, all the ground lost having been reclaimed.
Not over one hundred lives are believed to have been lost by the blowing up of the mine.--The losses in Mahone's division are not over two hundred, killed and wounded.
Among the killed are Colonel Evans, 64th Georgia; Captain Ruth, commanding 22nd Georgia; Lieutenant-Colonel Williamson, 6th Virginia, slightly wounded.
The negroes fought quite well to-day, and charged, crying, "No quarter — remember Fort Pillow."
All quiet to-night. 