LETTER -- No. 40.

MOUTH OF FALSE WASHITA.

Since I wrote my last Letter from this place, I have been detained here with the rest of the cavalcade from the extraordinary sickness which afflicting the regiment, and actually threatening to arrest its progress.

It was, as I wrote the other day, the expectation of the commanding officer that we should have been by this time recruited and recovered from sickness, and ready to start again on our march; but since I wrote nearly one half of the command, and included amongst them, several officers, with General Leavenworth, have been thrown upon their backs, with the prevailing epidemic, a slow and distressing bilious fever. The horses of the regiment are also sick, about an equal proportion, and seemingly suffering with the same disease. They are daily dying, and men are calling sick, and General Leavenworth has ordered Col. Dodge to select all the men, and all the horses that are able to proceed, and be off to-marrow at nine o'clock upon the march towards the Camanchees, in hopes thereby to preserve the health of the men, and make the most rapid advance toward the extreme point of destination.

General Leavenworth has reserved Col. Kearney to take command of the remaining troops and the little encampment; and promises Colonel Dodge that he will himself be well enough in a few days to proceed with a party on his trail and overtake him at the Cross Timbers.

I should here remark, that when we started from Fort Gibson, the regiment of dragoons, instead of the eight hundred which it was supposed it would contain, had only organized to the amount of 400 men, which was the number that started from that place; and being at this time- half disabled, furnishes but 200 effective men to penetrate the wild and untried regions of the hostile Camanchees. All has been bustle and confusion this day, packing up and preparing for the start to-marrow morning. My canvass and painting apparatus are prepared and ready for the packhorse, which carries the goods and chattels of my esteemed companion Joseph Chadwick and myself, and we shall be the two only guests of the procession, and consequently the only two who will be at liberty to gallop about where we please, despite military rules and regulations, chasing the wild herds, or seeking our own amusements in any such modes as we choose. Mr. Chadwick: is a young man from St. Louis, with whom I ham been long acquainted, and for whom I have the highest esteem. He has so far stood by me as a faithful friend, and I rely implicitly on his society during this campaign for much good company and amusement. Though I have an order from the Secretary at War to the commanding officer, to protect and supply me, I shall ask but for their Protection ; as I have, with my friend Joe, laid in our own supplies for the campaign, not putting the Government to any expense on my account, in pursuit of my own private objects.

I am writing this under General Leavenworth's tent, where he has personally invited me to take up my quarters during our encampment here, and he promises to send it by his express, which starts to-marrow with a mail from this to Fort Towson on the frontier, some hundreds of miles below this. At the time I am writing, the General lies pallid and emaciated before me, on his couch, with a dragoon fanning him, whilst he breathes forty or fifty breaths a minute, and writhes under a burning fever, although he is yet unwilling even to admit that he is sick.

In my last Letter I gave a brief account of a buffalo chase, where General Leavenworth and Col. Dodge took parts, and met with pleasing success. The next day, while on the march, and a mile or in advance of the regiment, and two days before we reached this place, General Leavenworth, Col. Dodge, Lieut. Wheelock and myself were jogging along, and all in turn complaining of the lameness of our bones, from the chase on the former day, when the General, who had long ago had his surfeit of pleasure of this kind on the Upper Missouri, remonstrated against further indulgence, in the following manner: "Well, Colonel, this running for buffaloes is bad business for us -- we are getting too old, and should leave such amusements to the young men; I have had enough of this fun in my life, and I am determined not to hazard my limbs or weary my horse any more with it -- it is the height of folly for us, but will do well enough for boys." Col. Dodge assented at once to his resolves, and approved them; whilst I, who had tried it in every form! and I had thought, (to my heart's content), on the Upper Missouri, joined my assent to the folly of our destroying our horses, which had a long journey to perform, and agreed that I would join no more in the buffalo chase, however near and inviting they might come to me.

In the midst of this conversation, and these mutual declarations (or rather just at the end of them), as we were jogging along in "Indian file", and General Leavenworth taking the lead, and just rising to the top of a little hill over which it seems he had had an instant peep, he dropped himself suddenly upon the side of his horse and wheeled back ! and rapidly informed us with an agitated whisper, and an exceeding game contraction of the eye, that a snug little band of buffaloes were quietly grazing just over the knell in a beautiful meadow for running, and that if I would take to the left ! and Lieut. Wheelock to the right ! and let him and the Colonel dash right into the midst of them; we could play the devil with them!! One half of this at least was said after he had got upon his feet and taken off his portmanteau and valise, tn which we had all followed suit, and were mounting for the start! And I am almost sure nothing else was said, and if it had been I should not have heard it, for I was too far off! and too rapidly dashed over the waving grass! and too eagerly gazing and plying the whip, to hear or to see, anything but the trampling hoofs ! and the blackened throng I and the darting steeds ! and the flashing of guns ! until I had crossed the beautiful lawn ! and the limb of a tree, as my horse was darting into the timber, had crossed my horse's back, and had scraped me into the grass, from which I soon raised my head ! and all was silent ! and all out of sight! Save the dragoon regiment, which I could see in distance creeping along on the top of a high hill. I found my legs under me in a few moments, and put them in their accustomed positions, none of which would for some time, answer the usual purpose; but I at last got them to work, and brought ("Charley") out of the bushes, where he had "brought up" in the top of a fallen tree, without damage.

No buffalo was harmed in this furious assault, nor horse nor rider. Col. Dodge and Lieut. Wheelock had joined the regiment, and General Leavenworth joined me, with too much game expression yet in his eye to allow him more time than to say, "I'll have that calf before I quit!" And away he sailed, "up hill and down dale," in pursuit of a fine calf that had been hidden on the ground during the chase, and was now making its way over the prairies in pursuit of the herd. I rode to the top of a little hill to witness the success of the General's second effort, and after he had come close upon the little affrighted animal, it dodged about in such a manner as evidently to baffle his skill, and perplex his horse, which at last fell in a hole, and both were instantly out of my sight. I ran my horse with all Possible speed to the spot, and found him on his hands and knees, endeavouring to get up. I dismounted and raised him on to his feet, when I asked him if he was hurt, to which he replied "No, but I might. have been," when he instantly fainted, and I laid him on the grass. I had left my canteen with my portmanteau, and had nothing to administer to him, nor was there water near us. I took my lancet from my pocket and was tying his arm to open a vein, when he recovered, and objected to the operation, assuring me that he was not in the least injured. I caught his horse and soon got him mounted again, when we rode on together, and after two or three hours were enabled to join the regiment.

From that hour to the present, I think I have seen a decided change in the General's face; he has looked pale and feeble, and been continually troubled with a violent cough. I have rode by the side of him from day to day, and he several times told me that he was fearful he was badly hurt. He looks very feeble now, and I very much fear the result of the fever that has set in upon him.

We take up the line of march at bugle-call in the morning, and it may be a long time before I can send a Letter again, as there are no post-offices nor mail carriers in the country where we are now going. It will take a great deal to stop me from writing, however, and as I am now to enter upon one of the most interesting parts of the Indian country, inasmuch as it is one of the wildest and most hostile, I shall surely scribble an occasional Letter, if I have to carry them in my own pocket. and bring them in with me on my return.