Shortly after the battle of Fair Oaks, the new and vastly more provident, liberal, and wisely economical policy introduced into the medical service, with the appointment of Dr. Hammond as Surgeon-General, and of the new corps of Medical Inspectors, began to be felt in the army of the Potomac,—and although many of the agents necessary to the perfect success of that policy were unable at once to accommodate their habits to the required change, the Commission, scrupulously adhering to its purpose to do nothing which the properly responsible officials in any department evinced any readiness to do without its assistance, had the satisfaction of seeing the necessity for its special service, in connection with the hospital transports, grow gradually smaller and smaller. Under the dry, taciturn, and impenetrable manner, promising nothing, of the new Medical Director of the Army of the Potomac, who, just after the battle of the Seven Days, relieved a predecessor of precisely the opposite qualities, was found to be concealed some influence by means of which whatever had before been impossible began to be thought possible, and to be tried for, after a few judicious dismissals had been made; and, after a few visits of influential friends to Governors and Senators in behalf of the dismissed had resulted in nothing but an incomprehensible failure of their purpose, the Commission's occupation was more than half gone with that army. But where so many agents are to be depended on, and such sudden new dispositions and reorganizations must be made, as after those terrible seven days, it is impossible that any demand of a large army should always be promptly and fully met. Anxiety for the well, that they might be saved from disease, soon outweighed anxiety lest the sick should not be tenderly cared for, and in more than one direction an opportunity was found to supply temporary deficiencies, which otherwise would have told severely upon the health of many thousand men. During the month after the army reached and intrenched itself on the James River, the vessels managed by the Commission probably did a better service in what they brought to the army, than in the comfort they secured to the sick who were sent away upon them. The following extracts will serve to give the reader a more complete understanding of its ruling spirit and purpose, and show its continued action to the time of the withdrawal of the army of the Potomac from the Peninsula.

(A.) Norfolk, June 30, 1862.—We were driven from White House Friday P. M.; arrived at Old Point yesterday. Being unable to get coal there, came here this evening. Shall coal to-night and leave at daybreak for Harrison's Bar, on James River, where the gunboats are said to be. We hope to get further up, but are advised by General Dix that we cannot safely attempt it at present.

(A.) Off Berkeley, James River, July 1, 1862.—We felt our way up the river slowly, and with some difficulty, having no pilot, and seeing no vessel under way after passing out of sight of Newport's News until we reached this point. Here there was a gunboat and three small steam-transports, each of which afterwards left, so that for a short time we were alone. Transports soon began to come up, however, and to-night there are a dozen or more about us.

We have Colonel ——, Colonel ——, and a few other wounded officers on board. They were sent to us by General McClellan's own ambulance, half an hour after we arrived. The General had been here, and left only as we were coming to the wharf. The officers he saw here converse with us freely, and we have had officers on board from most of the army corps, who have also talked, apparently without reserve, with us. Yet reports and opinions are so contradictory, that we are in singular uncertainty as to what has happened and as to what we have to expect

The officers and soldiers all show the influence of intense excitement; they acknowledge the gravest anxiety; they are terribly fatigued, yet generally seem in good spirits. They speak much of the bravery of the men.

(A.) Chesapeake Bay, July 4, 1862.—I left our anchorage off Head-quarters of the Army of the Potomac, where I wrote you last, about four o'clock yesterday afternoon, and am running to Washington, by request of the Medical Director, to advise the Surgeon-General of the sanitary condition of the army, and to secure the immediate supply, as far as possible, of its most urgent surgical and medical wants. As the rebels have put out the lights, and we could get no pilot, we were all night feeling our way down the river, and shall not be able, with all we can do, to get to Washington till late to-night. I hope to get what is most necessary, and leave on our return before night to-morrow. I telegraphed from Old Point to have everything advanced.

I have seen and conversed freely with many staff officers, and been among the men, wounded and well—if any can be called well, where all are feverish with seven days and nights of fatigue and exhaustion and starvation and excitement. One, a Major-General, said, "I have not been asleep, nor have I tasted food, in five days. I have only sustained myself with coffee and cigars." As to the men, the following is a fair sample of statements commonly made: "My regiment has had, for the last five days before arriving here, two days' rations; what has been eaten of this has been uncooked; during that time it has made five hard marches, and fought five battles; one third of it has fallen in killed or wounded, and not one man has been shot in the back. One third of what remains is now on picket duty in the woods, which the enemy is shelling; the other lies yonder, in the mud, sleeping on its arms." This was during the rain, which fell in such torrents day before yesterday. Yesterday the enemy was attacking again, and the whole army in the line of battle up to the time we left.

The exultant confidence of the army in itself is beyond all verbal expression. It has grown out of the experience of its ability to resist and foil and terribly punish desperate assaults made upon it, as is supposed with forces greatly superior in number. It says, proudly, "All that men can do, we can do." But there is also the consciousness of a terrible strain upon its energies, of an unnatural strength, and the reflection is frequent that there must be a limit to every man's endurance.

Rest and recuperation,—how are they to be had? The first only by the relief of reinforcements; the second only by good diet and favorable hygienic circumstances. Eastern Virginia is all malarious,—the banks of James River notoriously so; the army is chiefly upon a moderately elevated, slightly undulating table-land; the river on the south side; swampy ground at no great distance on the other sides. It is open, airy, dry,—a healthful point, upon the whole, as any that could be selected east of Richmond. But the sun will lie exceedingly fierce upon it, and it is supposed the army has lost two thirds of its tents. Probably a majority of the men have lost also their knapsacks and blankets. Many were without caps or shoes. The area held is small, and will be crowded. If the enemy is active, as it would appear his policy to be, the officers will be too much occupied with the immediate military necessities of the position to give much attention to police duties. Even if they should be well disposed, the excessively fatigued and exhausted condition of the men, and the necessity of reserving their strength from day to day for the struggle with the enemy, will forbid the constant labor which would be necessary to prevent a terrible accumulation of nuisances, until at least reinforcements shall arrive so large that no more than the ordinary quotas will be required for guard and picket duty. After such tension and trial, a rapid reduction of force must also occur from sickness, and those not on the sick-list will suffer from the lassitude of reaction from excitement. Under these circumstances, all our experience shows that it will be hardly possible to enforce requirements, the observance of which must be essential to a healthy camp.

Unless large reinforcements speedily arrive, then, not only must the army feel that its heroism is unappreciated, and the object for which it struggled is to be lost by the neglect of others, and thus become dejected, dispirited, and morally resistless to the dangers of disease; but it will be physically impossible to establish such guards against these dangers as are most obviously and directly called for.

There is, in general, a large degree of confidence that, with the aid of the gunboats, which are throwing shell on the flanks at frequent intervals, we can hold the position till sufficient reinforcements come to place it beyond question; but no one speaks with entire confidence, and the nearer to the head the graver seems the apprehension,—though with all there is that strange exultation—ready to break out in laughter, like a crazy man's. There are some few who are utterly despondent and fault-finding. But there is less of this than ever before, and fewer stragglers and obvious cowards,—nothing like what was seen after Pittsburg Landing. Of what we saw after Bull Run there is not the slightest symptom. In short, we have then a real grand army, tried, enduring, heroic,—worth all we can give to save it.

(C.) On Saturday we commenced the distribution of the cargo, and it has been going steadily on since in a very gratifying manner, every one concerned throwing off his coat, and working with a will, these intensely hot days,—surgeons, quartermasters, and other officers, always giving us every possible assistance in their eagerness to get this agreeable addition to their fare into the camp-kettles as soon as possible. The salted fish was a grand hit. It seems to have a peculiar attraction for languid appetites this hot weather. We have met, thus far, with but one man inclined to throw any obstruction in the way of the distribution,—a brigade commissary, who seemed to think any unusual indulgence of a soldier's whims of appetite must be demoralizing. Word of our intention had gone through the brigade, however, before he interfered, and the eagerness of the surgeons and of the soldiers took him very quickly out of the way without any efforts on our part. Regimental transportation was quickly at the wharf, with the thanks and compliments of the colonels, and each received its quota.

... The promptness with which the cargo—nearly a thousand barrels—would have been discharged, will be somewhat affected by the inability of some of the regiments of Heintzelman's corps to send transportation, on account of a movement for which they are ordered to stand in readiness to-day.... The sudden orders given yesterday for the immediate transportation of several thousand sick, have caused an influx of sick to the landing, overrunning all that the exertions of the Medical Director could do to provide for them.... This morning we found five hundred and sixty convalescents on board the transport Cahawba, with, to use the language of the ——, "not a bit of a thing aboard for 'em to chaw upon." As the poor fellows, many of them just getting up from fever, had been, in most cases, finding their way from the camps to the landing on foot, during the night, their want was urgent. Fortunately, we had a good supply of the concentrated beef of Martinez's preparation, and were not long in getting ready an excellent breakfast for them. It is in just such cases as this, where misery is massed, and where what is done tells not only for the relief of misery, but for the strength of the army and the putting down of the rebellion, that we find the greatest satisfaction in stepping in with the gifts of the people. Many of these men were in just the condition in which a set-back would be likely to lead to a relapse and lingering illness, and in which again, if they were well cared for, they might be built up rapidly, and soon be sent back to their muskets.

On account of the movements to-day, I shall ride out to the camps this afternoon, and make some change of arrangements for the further distribution of the anti-scorbutics. The gunboats were playing very lively at sunrise, a little way down the river. This is as much as I should say to-day, but you will hear of something that you hardly expect by the next mail-boat.