The steamship Adriatic has been, it is hoped, satisfactorily completed. She went down the bay on her first trial trip on Friday, the 13th inst. The morning was rainy, and this first spontaneous movement of the magnificent vessel attracted little attention, but the machinery appeared to work in every respect successfully. Much attention has been called to this ship by her large size, and the alterations which have been necessary in the construction of her engines. We intend to keep our readers informed of her progress until complete success has been established. -----------....----------- Another CmIet.A faint telescopic comet was discovered on tbe evening of the 12th inst., at the Observatory of Harvard College, by Mr. Horace P. Tnttle, near the star Theta Draconis. This comet is the sixth which has appeared in 1857. We believe it is the thirteenth or fourteenth discovered at this observatory, before any information had been received of their having been seen elsewhere. -------------.^-e------------- The steamship Arabia, which arrived at 1 this port on the morning of the 13th, brought the welcome news that Delhi was in the pos- Y) session of the British.