Yesterday George s/o late John JOHNSTON, Esq., Police Magistrate of (St. John) city and nephew of late Charles JOHNSTON, Esq., High Sheriff of City & Co. of St. John, who has for some time past been engaged in the shipping office at Reed's Point, left his home on Coburg St. to go down to town about half past 8 o'clock, but being seized with a sudden faintness, he returned and went into the store of D. SULLIVAN, Charlotte St. near Union, to sit down for a few minutes. Although he looked to be in his usual health, on saying that he felt weak and faint, Mr. S. offered him a glass of wine, but he shortly after became unconscious. His brother, Dr. JOHNSTON, and his mother were at once summoned, but he sank rapidly and Dr. HAMILTON was called in. He expired about 11 o'clock. It is supposed that heart disease was the cause of the sad event. FREE: He was about 25 years of age.