The measures for the improvement of the channel of this stream are now in progress, as we learn by the ' Baltimore American."— The dredging machine has been, since the 11th ult., excavating the bottom of the river at Sparrow Point knoll, the intention being to reduce the knolls nearest the main channel and bring them to a common level with the bed of the river, say eighteen feet, after which the commissioners will determine on the requisite additional machinery lor opening a channel, twenty-two feet deep, throughout the entire length ol the river.