On the 22nd August, she passed near the group of Rocky Islands, called Bassa da India, which are situated nearly in the middle of the channel, and pursued her voyage under sail. Of course, her progress was slow against an adverse wind, and no little anxiety was felt by her captain, on account of the uncertainty of the compasses, and their discrepancy with each other. She arrived, however, safely at Mozambique on the afternoon of the 31st, without having had occasion to use her engines, except just to carry her into the anchorage. As she passed through the outer roads, she communicated with H.M. brig Acorn, Captain Adams, which was on the look-out for two slavers daily expected to arrive for cargoes; and, the better to entrap them, she had hoisted a sort of decoy-flag at her main, which she had already taken from one of the same description. While a short visit was being paid on board, a pilot had come off from the shore, to conduct the Nemesis into the inner harbour, where she was soon brought to within a quarter of a mile of the town. Little time, however, could be spared for the visit, but there was still some necessary work to be done on board, which could not be completed until the following day. As the errors of the compasses have been alluded to above, and seem to have occasioned very great anxiety upon this passage, it may be well to make some remarks about them again in this place. It will be remembered, that before leaving Liverpool a long series of experiments had been made, which were intended to provide means of counteracting the local action of the iron of the ship's hull upon the compasses. But no worse place can be imagined than a crowded dock for the purpose of carrying on experiments of such nicety. Disturbing causes were continually operating, and the accident she met with on her way to Portsmouth proved that the correctness of the compasses was very far from being satisfactory. The experiments which were afterwards made at Portsmouth were also very doubtful in their result, in all probability owing, as before explained, to the absence of the boxes of chain or broken iron, which are always used by Professor Airy. It may readily be imagined that the utmost anxiety was always felt on board the vessel on this account, particularly when near the land; and many a long and anxious night has been spent on deck, with frequently a leadsman upon each of the paddle-boxes, to take soundings, and one in the bowsprit besides.