Coroner Earle held an inquest at Black River (St. John) on the body of William James WAGNER, nine year old son of Mrs. WAGNER widow of Capt. WAGNER. On Wednesday morn. about 9 o'clock, Daniel KYFFIN, a farm hand in the employ of Mrs. Wagner started out in a boat with young Wagner and another lad named George AMBROSE, ten years of age, to obtain sea weed which is used along the shore as fertilizer. Mrs. Wagner, from the door of her house which is situated only a short distance from the mouth of Black River, saw the three put off in the boat. Exactly what occurred after the boat put off will never be known as all three perished. Mrs. Wagner is the wife of the late commander of the lost barquw "Ada Barton". He died quite recently of yellow fever in the West Indies. Thomas KYFFIN of Portland is a brother of the drowned man who was 45 years of age and unmarried.