... I MA1?1rET HERALD. Cott? EXCHANS, MondayJluie 15, 181!. A sbort, supply of Wheat, and the attendance of a great number of buyers, occasioned acconsiderable advance ill the prices of this article, but more particularly Fso i the disposal of finc sa.ples, aud to which we can hardly fix a currency.- Flour, since out last, has been settled at tt;5s. per sack, and to-day 5s. per sack more was ?? ...