A sad accident occurred in St. John Monday afternoon by which two young girls named Mary ALLEN and Mary CAPLES were drowned. They, in company with two other girl friends, went bathing in what is known as Leonard's creek and by some means got beyond their depth, and before assistance could be had, both perished. A Mr. STEVENSON, whose daughter was one of the party, happened to be near and succeeded in saving her and a Miss ALLEN, sister of the one drowned. Being unable to swim and having no apparatus, he was unable to rescue the drowning girls. The bodies were recovered about an hour after the accident.