I have written you a long dissertation on cavalry, which I dare say you will find contains nothing new to you; but the complaints which you make of deficient supply of horses have lately occupied much of my thoughts and time, and I have put on paper the considerations to which they have led me.

Colonel Swords, chief quartermaster of the Western District, has been sent to Louisville to expedite this supply of horses to you, and whatever can be done will be done, but it is not possible to pick up 10,000 horses in a morning, and it will be long before you can get any such addition to your forces. Five thousand more horses are called for here to supply losses of an inactive winter, though a constant stream of horses has poured into Washington since the war began.

I have advised you to send cavalry officers to aid in the inspection, and thus keep up the standard. The quartermasters will take all fit horses offered them, but as for buying in open market, I have tried that here, and did not get a hundred.

I then gave public notice and gave out contracts, and supplied McClellan's army between Bull Run and Yorktown, 225,000 strong, with nearly one thousand pieces of artillery.

Men will not bring horses from a distance on the chance of sale; they must have fixed contracts on which they can rely before they will incur the risk and cover the country with agents to pick up horses. The Government cannot employ these numerous agents, who would run off with the funds or bring worthless horses. I have not the officers, and I cannot get from the generals commanding in the field even competent officers enough to supervise inspections at the depots. How, then, car I get the hundreds who would be needed to overrun the country and buy horses directly from the farmers? I might as well undertake to purchase each bushel of oats or ton of hay or barrel of flour from the particular farmer who sowed the seed.

Compel your cavalry officers to see that their horses are groomed; put them in some place where they can get forage, near the railroad, or send them to your rear to graze and eat corn. When in good order, start them, a thousand at a time, for the rebels' communications, with orders never to move off a walk unless they see an enemy before or behind them; to travel only so far in a day as not fatigue their horses; never to camp in the place in which sunset found them, and to rest in a good pasture during the heat of the day; to keep some of their eyes open night and day, and never to pass a bridge without burning it, as telegraph wire without cutting it, a horse without stealing or shooting it, a guerrilla without capturing him, or a negro without explaining the President's proclamation to him. Let them go any way so that it is to the rear of the enemy, and return, by the most improbable routes, generally aiming to go entirely round the enemy, and you will put Johnston and Bragg into such a state of excitement that they will attack or retreat to relieve themselves; they will not be able to lie still.

You gained a great success at Murfreesborough by your persevering courage and endurance. The same qualities will enable you to conquer in the next struggle, but this long inactivity tells severely upon the resources of the country. The rebels will never be conquered by waiting in their front. Operate on their communications; strike every detached post; rely more upon infantry and less upon cavalry, which in this whole war has not decided the fate of a single battle rising above a skirmish, which taxes the resources of the country, and of which we have now afoot a larger animal strength than any nation on earth. We