Our march lay through a fine and fertile section of country. The vast fields of grain are ripening for the harvest, and their appearance indicates that thus far the labors of the husbandman have not been in vain. The peacefulness of the fields and flocks presents a striking contrast to the warlike preparations which are now being made for what must be the most decisive and bloody contest of the war. The rebellion seems to have risked its very existence in the coming conflict, which cannot be many days hence. Determination and desperation seem foremost in the movement. On our side a solemn decision seems to be actuating the masses. We know that should the "Stars and Bars" be victorious again, and at this crisis of our national affairs, as they were at the two Bull Run battles, and at Chancellorsville, our "Stars and Stripes" will not only be shamefully humbled, but suffer cruel elimination. In such an event some of our stars must fall and some of the beams of our light must be obscured. "But conquer we must, for our cause it is just, And this be our motto, 'In God is our trust.' And the star-spangled banner in triumph shall wave O'er the land of the free and the home of the brave." _Sunday, June 28._--All night long we were on the march, arriving in the vicinity of Frederick City early in the morning. The whole country for miles seems to be covered with soldiers. This is one of the most beautiful spots in the world. However, the city does not show the thrift and prosperity which are evidenced in Northern cities enjoying similar advantages. This is the capital of Frederick County, one of the richest in the State. Looking southward from the city we behold an almost interminable stretch of beautiful rolling land, nearly every inch of which is not only arable but richly productive. On the east, at a distance of several miles, the eye rests upon a range of hills which sweep downward toward the Potomac, terminating in the lofty peak called Sugarloaf. Westward rises the loftier chain of the Catoctin, which is but a continuation of the Bull Run Mountains, severed by the river at Point of Rocks. All the highest peaks of these hills and mountains are now used for signal stations, where wave the signal flags by day and flash the signal fires by night. One seldom wearies in watching these operations, though he may not understand their significance. CHANGE OF COMMANDERS.