Indian Battle-Sroux City, August 19.—Iteportcomes from Fort SuIIv. this . vc* j* Ining, that the Indians, to 1 lie imm* i her of -1,000, attacked Guslar’s ex-1 pemlition, on the 15th, and were repulsed with heavy loss. Custar’s loss is reported to be 50 killed and ■ wounded. This report was'brought into Fort Sully, by a mail rider, who states that he met one ol’Custar’s scouts, and got the nows from him. _