ST. AGNES', ISLES OF SCILLY.—At 9 P.M., on the 21st March, signals were seen in St. Mary's Sound. In ten minutes the Life-boat James and Caroline was launched and proceeded to the spot, under sail, through a moderate sea, the wind blowing a strong breeze from N.E. The fishing lugger Lydia, of Porthleven, was found anchored near the N. end of Bartholomew Ledge, her foremast having been carried away. The Life-boat men assisted the crew and the fishermen were enabled to proceed to St. Mary's..