>From Jackson's Oxford Journal, Saturday, March 8, 1800; Issue 2445.   We are informed that on Thursday night the 27th ult. a barge belonging to Mrs. GRAIN , of this City, loaded with a valuable cargo of goods bound to London, caught fire, where she lay moored near Wallingford, and the boat and her lading would have been burnt, had she not been almost immediately sunk.  The fire broke out on a boat that lay alongside Mrs. GRAIN's barge, which instantly communicated to some straw packages on board; and, notwithstanding, the most immediate and active exertions on the part of Mrs. GRAIN's servants, the whole would have been consumed had they not had recourse to the above expedient made use of.  The damage done is not yet ascertained, but it will, we fear, be very considerable.