The steamer 'Avon,' in her surveying expedi tion the other day, did nob' get further up tho river than the submerged forest, which is a few miles 'further on from here, and through which a passage w ill have to Be made before boata of any n.xe can proceed. This, I anticipate, will bjs ii matter of no groat difficulty with the resources at commaud, and in a few days you may expect to hear of it being accomplished. We had a fall of rain this morning, but this afternoon tho clouds Have broken, and the sun shines forth again. While we have boon enjoying the late fine weather as a great comfort to camp life, still at the same time it could not be for gotten that it was having its effect upon the river — that great and important means of tons port. This effect has been perceptible daily, and the navigation becomes more and more dilHcult every day. The 'Pioneer' was lato in arriving last night owing to this cause, and then, when \\ ithin a short distance of the landing place", unfortunately took the ground, her cargo was taken out in boats, and she left for the Bluff this morning without coming further up. Before making another trip up she will have been considerably lightened, and by the time, if it should arrive, that the necessity is urgent, it is to be hoped that the small steamers will have arrived from- Sydney. A jurther advance is meditated, and would have taken place this morning, but just as tho tents were struck, and all .ready to be put on board the boats, the rain came down in fine style, when tbe order was countermanded. I believe that the next camp ground will not be very far from here.butnearthesubtnergt'd forest, bo as to form a protection to the working pnrty. The redoubt on the hill has been completed, and is a very strong one, built with a greater regard to facility of defence than most of I hose that are scattered about the country. There are positions for guns, which command the principal approaches, and an enemy in the trench could be ensily dislodged. 