On reaching the river we found the two pontoon bridges over which already a large portion of our army had passed on before us. They had been much retarded by the heavy rains and mud. The approaches to the pontoons had been so trodden by the myriad feet of men and beasts, and cut by the heavy wheels of laden wagons and artillery, that we found the roads almost bottomless. But as we had seen mud many times before, we moved forward undismayed, though somewhat retarded, and were soon on Northern soil. A somewhat strange feeling came over us on finding ourselves marching mainly towards the North Star to meet the enemy, whereas we had so long been accustomed to look and march only southward for this purpose.

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.

This has been a day of much interest among us and of no little excitement—a day of changes and reorganization. An exciting rumor was bandied from man to man this morning, that General Hooker was about to be relieved from the command of the grand army; and the day was only partly spent when the strange rumor resolved itself into the astounding truth. The facts which led to this result may not be perfectly understood among us, but appear to be about as follows: On discovering that the enemy had actually invaded the Northern States, General Hooker requested the authorities to send him all the forces which could be spared from General Heintzelman's command in and about the Defenses of Washington. This was done. But, having crossed the Potomac, General Hooker visited Harper's Ferry with its strong garrison, and immediately urged upon the Government the importance of placing this force also under his command. Upon this subject there sprang up a sharp controversy between Hooker and Halleck. The latter rejoined to the former in these words:

"Maryland Heights have always been regarded as an important point to be held by us, and much expense and labor incurred in fortifying them. I cannot approve of their abandonment, except in case of absolute necessity."

General Hooker's reply to this shows him to have been in the right, and to have comprehended the relative importance of the position in question:

"I have received your telegram in regard to Harper's Ferry. I find ten thousand men here in condition to take the field. Here they are of no earthly account. They cannot defend a ford of the river; and, so far as Harper's Ferry is concerned, there is nothing of it. As for the fortifications, the work of the troops, they remain when the troops are withdrawn. This is my opinion. All the public property could have been secured to-night, and the troops marched to where they could have been of some service. Now they are but a bait for the Rebels, should they return. I beg that this may be presented to the Secretary of War, and his Excellency, the President."

Receiving no direct reply to this announcement, and goaded by the pressure of fast-moving events, our General yielded to do what many of us heartily condemn, by sending the following message: