In the spring of 1855, while the Crimean War was raging, the Government of the United States determined to send a military commission to Europe, to observe the warlike operations then in progress, to examine the military systems of the great Powers of Europe, and to report such plans and suggestions for improving the organization and discipline of our own army as they might derive from such observation. The officers selected for this trust were Major — now Colonel — Delafield, of the Engineers, Major Mordecai, of the Ordnance, and Captain McClellan. The last was by some years the youngest of the three, Colonel Delafield having been graduated at West Point in 1818, and Major Mordecai in 1823. The selection of so young a man for such a trust is a proof of the high reputation he had made for himself in the judgment of those by whom the choice was made; and it may be here mentioned that he was in the first instance designated for the commission by President Pierce himself, who had had an opportunity in the Mexican War to observe what manner of soldier and man ho was. Of the three officers, he, too, was the only one who had seen actual service in the field.  The exact nature of the duties assigned to the commission may be learned from the letter of the Secretary of War, the essential parts of which are as follows:--
The officers composing the commission sailed from Boston on the 11th of April. On arriving in England, they were courteously received by Lord Clarendon, Secretary of State for the Foreign Department,--Lord Panmure, the Secretary of War, being disabled by illness,--and furnished with letters of introduction to Lord Raglan, Sir Edward Lyons, the admiral of the Baltic fleet, and the officers in command at Constantinople. In France a difficulty arose on account of an imperative rule in the French military service that no foreign officer  could be permitted to go into their camp and afterwards to pass into that of the enemy, and that, therefore, it would be necessary for the members of the commission to give a promise that they would not go from the French camp to any other part of the Crimea, even although they might first go to St. Petersburg. This pledge the commission were not prepared to give, and the matter remained for some time in abeyance. But the most ample facilities were extended to them for visiting such military and naval establishments as they desired to inspect. On the 28th of May, the commission left Paris, intending to proceed to the Russian camp in the Crimea by the way of Prussia, starting first for Berlin, in order to confer with the Russian Minister in that city, Baron de Budberg, to whom the Russian Minister at Washington had given them a letter. Their object was to go from Berlin to the Crimea by the way of Warsaw and Kiev, on the Danube; and Baron de Budberg gave them passports and letters to Baron Krusentein, a Russian official at Warsaw. But on arriving at Warsaw they learned that no person there — not even the veteran hero Paskievitch, with whom they had an interview, and who treated them with much courtesy — had the power to grant them permission to go from Warsaw direct to the Crimea, and that there was nothing to be done but to proceed to St. Petersburg. During their stay in Warsaw, they examined the fortifications of that city and of Modlin. It was very annoying to the officers of the commission to find their progress blocked by ceremonials  and formalities which they might have escaped if they had been civilians and private citizens and gone direct from Constantinople to Sebastopol, as so many idlers and amateurs had done; but, having presented themselves in an official capacity, they could do no less than bear its burdens and encumbrances; and so they went on to St. Petersburg, where they arrived June 19. A few extracts from a letter written by Captain McClellan to his younger brother — now Captain Arthur McClellan--the day after his arrival in the Russian capital, give some of his first impressions of the country and people:--
We left Warsaw at six P. M. on the evening of the 13th, and reached here at about the same hour last evening, having travelled constantly day and night, merely stopping a few minutes for meals. In Poland the country is either flat or slightly rolling, the soil improving as you approach the Niemen, but in many places very poor. There are no towns of any consequence on the road, which, you will observe, passes near the Prussian frontier, but many villages, which are generally of wood and presenting a dirty, squalid appearance. The villages are mostly inhabited by Jews,--as dirty and wretched a race as you ever saw,--worse than any you ever saw. The appearance of the Poles is any thing but favorable; they look like a stupid, degraded race,--are dirty and ugly. It is difficult to imagine how they ever fought as they have done in the past. Ostrolinha was the site of a great battle in the revolution of 1831. It is a small wooden town on the Narew (Nareff), which is here a rapid stream some fifty yards wide. A large monument commemorates the victory gained by the Russians. Kouno is a town of good size, mostly built of plastered brick. A portion of it is very old, while the new suburbs  are handsome and well built. It presents the appearance of a flourishing place, there being many small vessels in the Niemen, and immense trains of carts constantly arviving here from the interior of Russia. They bring down tallow, hemp, &c., and carry back cotton, groceries, &c. As the Niemen empties in Prussian territory, a glance at the map will show you the importance of this place whilst the Russian ports are blockaded. The Niemen is here two hundred and twenty yards wide,--a bold and rapid stream, crossed by a raft-bridge. It was near and at this place that the great mass of the French army crossed the Niemen in June, 1812; and it was at the gate of this same town that in the retreat Marshal Ney fought so desperately, forming in his own person the rear-guard of the Grand Army. Of course I went to the spot during the short time we remained here. You now enter the great forests of Russia. As far as Vilkomir there is but little cultivation, the country being mostly covered by pine and beech forests. I should have mentioned that in the public square of Kouno there is a huge iron monument, bearing in Russian an inscription to the effect that out of seven hundred thousand French who crossed the Niemen in June, 1812, but seventy thousand recrossed in December. As far as Dunaburg (on the river Duna, or, as some of the maps have it, Dwina) the country is quite rolling,--almost broken; very different from the idea I had formed of it. You pass through a number of small towns and villages. Dunaburg appears to be a small town, presenting nothing of peculiar interest. There are some defensive works here. Before reaching Dunaburg, we passed through one town (a small one, perhaps hardly deserving the name of more than a village), called Novo Alexandrowsky, which is remarkably pretty. It is situated on the high banks of a large and handsome lake broken by little green islets. The houses and people were remarkably good-looking.  Rigitza is also a pretty little place: there is hero a ruined castle of long, long ago. Country now not so much rolling as near Dunaburg, but still by no means flat: it is fertile and well cultivated. Ostroff is another handsome little place: the road here crosses the river on a very fine suspension-bridge; and on an island in the river is a very extensive ruined castle, perhaps of some of the Teutonic knights. Pscov, near which we passed, seems to be especially blessed with churches, the gilded domes of which shone from afar. The country near here, and, in fact, from here to St. Petersburg, is low and level, the soil generally good,--sometimes poor, and sometimes very fertile. Pscov is the capital of a province, and at the head of a large lake. Near Ploosa is a swampy district of considerable extent, and many large lakes. Nothing of very great interest until one reaches Gatchina, where is the hunting-palace of the Emperor: it seems to be a very grand establishment. From there to this city the country is very flat, the soil not very good, but settlements increasing as you draw near. The general appearance of the portion of Russia I have seen is much superior to Chat of Poland; and I like the appearance of the people very much. * * * * * * * This is truly a most magnificent city,--wide streets, fine private houses, magnificent public buildings. Thus far I have, of course, merely had a glance at the exterior of things, and will not pretend to describe any thing, more than to say that it fully equals my expectations. We are very comfortably fixed at the Hotel de Russie,--good rooms, good meals, plenty of ice, &c. The road from Warsaw here is truly a magnificent one,--especially the portion of it in Poland. It is all macadamized; and they are now hard at work improving the Russian part, so that in a couple of months it will be throughout as fine a road, as any in the world. Think of  the immense length,--one thousand and seventy-four versts, or seven hundred and sixteen miles! So great is the traffic upon it at present that it is literally covered from one end to the other with trains of wagons passing in both directions. The trade which formerly passed down the Baltic now seeks its outlet into Prussia by this route. So great is this now that it seems hardly possible that Russia can feel the effect of the blockade very sensibly. New channels are opened, and immense additional numbers of men, animals, and capital are now employed in the land-transportation. * * * * * June 20 and 21, Midnight.--I write this paragraph in my room by the natural light,--no candle or any thing whatever: you may imagine the darkness of the night here.During their residence at St. Petersburg, the officers of the commission were treated with much courtesy by the civil and military authorities, and all possible facilities were afforded to them for examining the various military establishments in the vicinity. They were presented to the Emperor, at his request, and graciously received by him. But they did not succeed in obtaining permission to go to Sebastopol, because the officers in command there had requested that no strangers should be permitted to come there, as such visits occasioned them a great deal of embarrassment; and though the Emperor, of course, might overrule such objections, yet he felt bound to defer to the strongly-expressed wishes of officers placed in such responsible positions. Nothing could be urged in reply to this; and, disappointed as they were, they could not, as  military men, fail to respect the Emperor's deference to the views of his subordinates. On the 19th of July the commission proceeded to Moscow, and examined whatever was of interest in a military point of view there. Hastening back to St Petersburg, they left that city on the 2d of August, and arrived at Berlin on the 25th, having in the interval observed the fortifications and defences at Konigsberg, Dantzig, Posen, and Schwedt. At Berlin the various military establishments in that city and at Spandau were carefully inspected. From Berlin they determined to go to the Crimea by the way of Dresden, Laybach, Trieste, and Smyrna, and found themselves at last on the line of operations of the allied army at Constantinople, on the 16th of September. To the courtesy of the English naval authorities they were indebted for a passage in the first steamer that sailed for Balaklava, where they arrived on the morning of October 8. Here every possible facility and kindness, official and personal, was extended to them by the officers of the English army, including Sir George Simpson, the commander. It was hoped that the French Government would relax the rule they had laid down in the spring; but the new authorization to visit their camps and army, received at Balaklava, contained substantially the same condition as had been before exacted, and the commission could not avail themselves of the permission to which such terms were attached. The result was that they confined their examination to the camps, depots, parks, workshops, &c. of the English, Sardinian,  and Turkish armies, never entering the French camps in the Crimea except on visits of courtesy. On the 2d of November they left Balaklava in an English steamer, and spent some days in Constantinople and Scutari, inspecting the hospitals and depots of the allies. From Constantinople they proceeded to Vienna, examining on their route the defences of Varna and the remarkable triumphs of civil engineering in the works on the Soemmering Railroad. On the 16th of December they reached Vienna, and spent some days in a careful observation of the Austrian military establishments, and, after leaving Vienna, went to Venice, Verona, Mantua, and Milan, examining the military and naval establishments in each place. At Verona they were most kindly received by the veteran hero Marshal Radetzky, who contributed in every way to the attainment of their wishes as well as to their personal gratification. Colonel Delafield--from the introduction to whose Report this account of the movements of the commission is abridged — speaks in the warmest terms of the peculiar and uniform courtesy extended to them by the authorities and functionaries of Austria. That Government seemed to have quite forgotten the Martin Koszta affair. On the 2d of February, 1856, they arrived at Toulon, and, with the authority previously obtained from the French Government, examined the military and naval defences of that important depot. But the only facility extended to them was that  afforded by a printed ticket of admission transmitted from Paris, which did no more than command the services of a porter to conduct them through the buildings, docks, and vessels, and gave them no opportunity to converse with any of the officers. From Toulon they visited in succession Marseilles, Lyons, Belfort, Strasbourg, Rastadt, Coblentz, and Cologne, observing their fortresses and defences,--in the last three places, however, without the advantage of any special authority. The 24th and 25th of February were spent at Liege, where their time was occupied at the national foundry for artillery and another for smallarms, both on a more extended scale than any corresponding establishments in Europe at that time. On the 1st of March the commission was at Paris again. Two days were devoted to an examination of the fortress at Vincennes; and several of the military establishments in Paris were also inspected. They were unable, however, to obtain the requisite authority for seeing those relating to the artillery. On the 18th of March the commission proceeded to Cherbourg and examined the works there. On the 24th of March they arrived at London, and afterwards visited the arsenal and dockyards at Woolwich, the vessels at Portsmouth, and the defences near Yarmouth, on the Isle of Wight, receiving every courtesy and facility they could desire from the military and naval officers at those stations in furthering the object of their visit. On the 19th of April they embarked for home. The above is a brief record of the labors of a  very busy year, in which, however, much precious time was lost from delay in obtaining the necessary official permissions to inspect military establishments. And it must be added that in many cases the commission failed to receive those facilities which assuredly would have been extended in our country to a similar board sent from any Government in Europe. It may be too much to expect that nations should be governed in their relations towards each other by the precepts of Christian morality, but surely it is not too much to ask that they should conform to the code of courtesy and good breeding recognized among gentlemen in the intercourse of social life. After their return, each of the officers upon the commission made a report to the Secretary of War of the results of their tour of observation; and these reports were in due time officially published by Congress in a quarto form, and pretty widely distributed. They were recognized by all competent judges as productions of great merit, reflecting the highest credit upon their respective authors, and amply vindicating the sagacity of the Government which selected them. In October, 1861, Captain McClellan's report was republished by the publishers of the present work, in an octavo volume, with illustrations, with the title, “The Armies of Europe: comprising Descriptions in detail of the Military System of England, France, Russia, Prussia, Austria, and Sardinia, adapting their Advant<*>ges to all Arms of the United States Service, and embodying the Report of Observations in  Europe during the Crimean War, as Military Commissioner from the United States Government in 1855-56.” Its contents are as follows. The first thirty-five pages are occupied with an able and interesting summary of the warlike operations in the Crimea, in which the plans and movements both of the Russians and the allies are criticized without a touch of arrogance, and yet with a manly decision of tone which reveals a sound military judgment and thorough military training. It merits can be fully perceived only by a professional reader; bat the general reader cannot fail to recognize in it the marks which show the writer to be a man of vigorous understanding and excellent powers of observation, as well as an accomplished officer. The style is simple, perspicuous, and direct, the style of Washington, Collingwood, and Wellington;--in other words, that good style which a man of sense will always write who has something to say and writes on without thinking about his style at all. As the work. from the nature of its contents, can never have been generally read, two extracts from this portion of the volume are hero appended,--enough, it is believed, to justify the commendation which has been bestowed upon it. The first is a brief criticism of the defences of Sebastopol:--
From the preceding hasty and imperfect account of the defences of Sebastopol, it will appear how little foundation there was for the generally received accounts of the stupendous dimensions of the works, and of new systems of fortifications brought into play. The plain truth is  that these defences were simple temporary fortifications of rather greater dimensions than usual, and that not a single new principle of engineering was there developed. It is true that there were several novel minor details, such as the rope mantelets, the use of the iron tanks, &c.; but the whole merit consisted in the admirable adaptation of well-known principles to the peculiar locality and circumstances of the case. Neither can it be asserted that the plans of the various works were perfect. On the contrary, there is no impropriety in believing that, if Todtleben were called upon to do the same work over again, he would probably introduce better close-flanking arrangements. These remarks are not intended to, nor can they, detract from the reputation of the Russian engineer. His labors and their results will be handed down in history as the most triumphant and enduring monument of the value of fortifications, and his name must ever be placed in the first rank of military engineers. But, in our admiration of the talent and energy of the engineer, it must not be forgotten that the inert masses which he raised would have been useless without the skilful artillery and heroic infantry who defended them. Much stronger places than Sebastopol have often fallen under far less obstinate and well-combined attacks than that to which it was subjected. There can be no danger in expressing the conviction that the siege of Sebastopol called forth the most magnificent defence of fortifications that has ever yet occurred.The next is a description of the final assault:--
A few minutes later than the assault upon the Malakoff, the English attacked the Redan. The Russians being now upon the alert, they did not pass over the open space before them without loss; but the mass succeeded in crossing the ditch and gaining the salient of the work.  Finding themselves entirely unsupported, they at once took shelter behind the traverses, whence the example and efforts of their officers did not avail to draw them, in order to occupy the work closing the gorge. Having in vain used every effort, having despatched every officer of his staff to the rear urging that supports should be at once sent up, and seeing that the Russians were now beginning to assemble in force, the commander of the English storming party reluctantly determined to proceed himself to obtain reinforcements. Scarcely had he reached the trenches, and at last obtained authority to move up the required succor, when, upon turning to lead them forward, he saw the party he had left in the work rapidly and hopelessly driven out at the point of the bayonet. No further effort was made to carry the work. It would, in all probability, have failed, and would only have caused a useless sacrifice of men. The failure of the English assault may be attributed partly to the fact that their advanced trenches were too small to accommodate the requisite force without confusion, in part to their not being pushed sufficiently near the Redan, but chiefly to that total absence of conduct and skill in the arrangements for the assault which left the storming party entirely without support. Had it been followed at once by strong reinforcements, it is almost certain that the English would have retained possession of the work. The two French attacks on the west of the central ravine were probably intended only as feints: at all events, the parties engaged were soon driven back to their trenches with considerable loss, and effected nothing. Their attempts upon the Little Redan, and the works connecting it with the Malakoff, met with even less success than the English assault. The Russians repulsed the French with great loss, meeting with the bayonet the more adventurous men who reached the parapet. Thus, in five  points out of six, the defenders were fully victorious; but, unfortunately for them, the sixth was the decisive point. In their admirable arrangements for the attack of the Malakoff, the French counted on two things for success:--first, they had ascertained that the Russians were in the habit of relieving the guard of the Malakoff at noon, and that a great part of the old guard marched out before the new one arrived, in order to avoid the loss which would arise from crowding the work with men; in the second place, it was determined to keep up a most violent vertical fire until the very moment of the assault, thus driving the Russians into the bomb-proofs, and enabling the storming party to enter the work with but little opposition. The hour of noon was therefore selected for the assault, and the strong columns intended for the work were at an early hour assembled in the advanced trenches, all in admirable order, and furnished with precise instructions. The mortars maintained an unremitting fire until the moment appointed. The very instant the last volley was discharged, the storming party of Zouaves rushed over the thirty paces before them, and were in the work before the astonished Russians knew what had happened. It was stated that this party lost but eleven men in entering the work. Other troops advanced rapidly to the support of the storming party, a bridge was formed by rolling up five ladders with planks lashed to them, a communication was at once commenced between the advanced trench and the bridge, brigade after brigade passed over, the redoubt was at once occupied by the storming party, and thus the Malakoff, and with it Sebastopol, was won. The few Russians remaining in the work made a desperate resistance. Many gallant attempts were made by Russian columns to ascend the steep slope in rear and regain the lost work; but the road was narrow, difficult, and obstructed, the position strong, and the French in force. All their furious efforts were in vain, and the Malakoff  remained in the possession of those who had so gallantly and skilfully won it. With regard to the final retreat to the north side, it can only be said that a personal examination of the locality merely confirms its necessity, and the impression so generally entertained that it was the finest operation of the war: so admirably was it carried out that not a straggler remained behind; a few men so severely wounded as to be unfit for rough and hurried transportation were the sole ghastly human trophies that remained to the allies. The retreat, being a more difficult operation than the assault, may be worthy of a higher admiration; but the Russian retreat to the north side and the French assault upon the Malakoff must each be regarded as a masterpiece of its kind, deserving the closest study. It is difficult to imagine what point in either can be criticized; for both evinced consummate skill, discipline, coolness, and courage. With regard to the artillery, I would merely remark that the Russian guns were not of unusual calibre, consisting chiefly of twenty-four-, thirty-two-, and forty-two-pounders, and that the termination of the siege was mainly due to the extensive use of mortars finally resorted to by the allies. If they had been employed in the beginning as the main reliance, the siege would have been of shorter duration. The causes of the unusual duration of this siege naturally resolve themselves into three classes: the skilful disposition of the Russians, the faults of the allies, and natural causes beyond the control of either party. Among the latter may be mentioned the natural strength of the position and the severity of the winter. In the first class there may be alluded to:--the skill with which the Russian engineers availed themselves of the nature of the ground; the moral courage which induced them to undertake the defence of an open town with a weak garrison; the constant use they made of sorties, among which  may properly be classed the battles of Balaklava, Inkermann, and the Tchernaya; the ready ingenuity with which they availed themselves of the resources derived from the fleet; the fine practice of their artillery; their just appreciation of the true use of field-works, and the admirable courage they always evinced in standing to their works, to repel assaults at the point of the bayonet; the employment of rifle-pits on an extensive scale; finally, the constant reinforcements which they soon commenced receiving, and which enabled them to fill the gaps made in their ranks by disease and the projectiles of the allies. The evidences of skill on the part of the allies, as well as the apparent faults on all sides, having been already alluded to, it is believed that the means have been furnished to enable any one to draw his own conclusions as to the history of this memorable passage of arms.Next after the observations on the Crimean War follow twenty pages on the European engineer troops, to which succeed twenty-eight pages on the French, Austrian, Prussian, and Sardinian infantry. A brief description of the French Zouave will be of interest to the reader:--
The dress of the Zouave is of the Arab pattern: the cap is a loose fez, or skull-cap, of scarlet felt, with a tassel; a turban is worn over this in full dress; a cloth vest and loose jacket, which leave the neck unencumbered by collar, stock, or cravat, cover the upper portion of his body, and allow free movement of the arms; the scarlet pants are of the loose Oriental pattern, and are tucked under gaiters like those of the foot rifles of the guard; the overcoat is a loose cloak, with a hood; the chasseurs wear a similar one. The men say that this dress is the most convenient possible, and prefer it to any other. The Zouaves are all French; they are selected from  among the old campaigners for their fine physique and tried courage, and have certainly proved that they are what their appearance would indicate,--the most reckless, self-reliant, and complete infantry that Europe can produce. With his graceful dress, soldierly bearing, and vigilant attitude, the Zouave at an outpost is the beau-ideal of a soldier. They neglect no opportunity of adding to their personal comforts: if there is a stream in the vicinity, the party marching on picket is sure to be amply supplied with fishing-rods, &c.; if any thing is to be had, the Zouaves are quite certain to obtain it. Their movements are the lightest and most graceful I have ever seen; the stride is long, but the foot seems scarcely to touch the ground, and the march is apparently made without effort or fatigue. The step of the foot rifles is shorter and quicker, and not so easy and graceful. The impression produced by the appearance of the rifles and of the Zouaves is very different: the rifles look like active, energetic little fellows, who would find their Best field as skirmishers; but the Zouaves have, combined with all the activity and energy of the others, that solid ensemble and reckless dare-devil individuality which would render them alike formidable when attacking in mass, or in defending a position in the most desperate hand-to-hand encounter. Of all the troops that I have ever seen, I should esteem it the greatest honor to assist in defeating the Zouaves. The grenadiers of the guard are all large men, and a fine-looking, soldierly set.Two hundred and ten pages — nearly one-half of the whole volume, the Appendix included — are next given to the Russian army, its organization, recruiting, rations, &c.  The following is a description of the Russian Cossacks:--
There are two peculiarities which cannot fail to arrest the attention and command the reflection of the observer of the Russian cavalry: these are, the general division of the cavalry into regulars and irregulars; and the corps of dragoons. The irregulars may be comprehended in the general name of Cossacks. Yet their peculiarities of armament, costume, and action are as varied as their origin; while the sources of the latter are as multifarious as the tribes which compose the mass of Russian nationality, and the circumstances which, through centuries of warfare, have finally united into one compact whole a multitude of conflicting and heterogeneous elements. But, with all this diversity, there are important and peculiar characteristics which pervade the mass, and are common to every individual, with as much uniformity and certainty as that with which the firm government of the Czar is now extended over them. These peculiarities are: intelligence, quickness of vision, hearing, and all the senses; individuality; trustworthiness on duty; the power of enduring fatigue, privation, and the extremes of climate; great address in the use of weapons; strong feeling for their common country; caution, united with courage capable of being excited to the highest pitch: in short, the combination of qualities necessary for partisan troops. The events of more than one campaign have proved, besides, that these irregulars can be used successfully in line against the best regular cavalry of Europe. Circumstances of geography and climate have given to these men a race of horses in every way adapted to their riders; the Cossack horse is excelled by none in activity and hardiness. The Cossack neglects no opportunity of feeding his  horse; during short halts, even under fire, he gives him whatever is to be had; the horse refuses nothing that is offered him, and eats whenever he has the opportunity, for he has not acquired the pernicious habit of eating only at regular hours. Some idea may be formed of the power of endurance of the Cossacks and their horses from the fact that, in a certain expedition against Khiva, there were three thousand five hundred regular Russian troops and twelve hundred Cossacks: of the regulars but one thousand returned, of the Cossacks but sixty perished. The tendency of events, during the present century, has been to assimilate the organization of the Cossacks to that of the regulars, to a certain extent: whether the effect of this has been to modify or destroy their valuable individual characteristics may yet remain to be proved in a general war; the events of the campaign of Hungary are said to indicate that more regularity of action has by no means impaired their efficiency. This brief description of the qualities of the irregular cavalry indicates at once the use made of them in war: they watch while the regulars repose. All the duty of advanced posts, patrols, reconnoissances, escorting trains, carrying despatches, acting as orderlies, &c., is performed in preference by the Cossacks: the consequence is, that, on the day of battle, the regular cavalry are brought upon the field in full force and undiminished vigor. Under cover of these active irregulars, a Russian army enjoys a degree of repose unknown to any other; while, on the other hand, it is difficult for their antagonists to secure their outposts and foil their stealthy movements. The rapidity and length of their marches are almost incredible; a march of forty miles is a common thing: they will make forced marches of seventy miles; in a thickly-settled country they have, in two days, made six marches of ordinary cavalry without being discovered. In concluding this subject, it is impossible to repress  the conviction that in many of the tribes of our frontier Indians, such as the Delawares, Kickapoos, &c., we possess the material for the formation of partisan troops fully equal to the Cossacks: in the event of a serious war on this continent, their employment, under the regulations and restrictions necessary to restrain their tendency to unnecessary cruelty, would be productive of most important advantages. In our contests with the hostile Indians, bodies of these men, commanded by active and energetic regular officers and supported by regular troops, would undoubtedly be of great service.The cavalry of Prussia, Austria, France, England, and the United States are next considered, the whole occupying about one hundred pages; and an Appendix, of the same extent, contains a system of regulations for the field service of cavalry in time of war. This arm engages the author's particular attention, naturally enough, as he was a captain of cavalry at the time. Besides its other merits, the volume is a record of the most faithful and persevering industry, and contains the results of an immense amount of hard work. It embraces accounts of military schools, forts, museums, camps, hospitals, and garrisons. The arms, dress, and accoutrements of the men, and the equipments of the horses, are minutely described, down to the most exact details. It is illustrated with several hundred engravings, making every thing plain to the eye where a visible representation is needed. In short, no one can look at this volume without seeing that the author has one of those happily constituted minds which neither over-looks  nor despises details, and yet is not so hampered by them as to be incapable of wide views and sound generalizations. No man can be a great officer who is not infinitely patient of details; for an army is an aggregation of details, a defect in any one of which may destroy or impair the whole. It is a chain of innumerable links; but the whole chain is no stronger than its weakest link. In January, 1857, Captain McClellan resigned his commission and retired from the army. He had then been fifteen years in the service,--years of busy activity and energetic discharge of professional duty. We may suppose him to have been moved to this step by the consideration that the future held out no promise of congenial employment and seemed to open no adequate sphere to honorable ambition. A dreary life upon some distant frontier, the monotonous discharge of routine duty, a renunciation of all the attractions of civilized life without the excitement of ennobling adventure or heroic struggle, presented an uninviting prospect to man like him, in the prime of early manhood, and with unworn energies alike physical and intellectual. lie thought, too, that in case of war his chances of occupation and promotion would be quite as good in civil life as if he had remained in the army. The rapid growth and material development of the country created a demand for capacities and accomplishments like his; and immediately upon his resignation he was appointed chief engineer of the Illinois Central Railroad, then just opened, and went to Chicago to reside.  In a few weeks he was made vice-president of the corporation, and took general charge of all the business of the road in Illinois. In this capacity he first made the acquaintance of Mr. Lincoln, now President of the United States, then a practising lawyer in Springfield, Illinois, and occasionally employed in the conduct of suits and other professional services on behalf of the company. In May, 1860, Captain McClellan was married to Miss Ellen Marcy, daughter of General R. B. Marcy, his former commander in Texas, and the chief of his staff during the Peninsular campaign. In August, 1860, he resigned the vice-presidency of the Illinois Central Road, in order to accept the presidency of the Ohio & Mississippi Railroad, which post he held, residing in Cincinnati, till the war broke out.