London, Thursday, May 6th, 1851.

"The World's Fair," as we Americans have been accustomed to call it, has now been open five days, but is not yet in complete order, nor anything like it. The sound of the saw and the hammer salutes the visiter from every side, and I think not less than five hundred carpenters and other artisans are busy in the building to-day. The week will probably close before the fixtures will have all been put up and the articles duly arranged for exhibition. As yet, a great many remain in their transportation boxes, while others are covered with canvas, though many more have been put in order within the last two days. Through the great center aisle very little remains unaccomplished; but on the sides, in the galleries, and in the department of British Machinery, there is yet work to do which another week will hardly see concluded. Meantime, the throng of visiters is immense, though the unexampled extent of the People's Palace prevents any crush or inconvenience. I think there cannot have been less than Ten Thousand visiters in the building to-day.

Of course, any attempt to specify, or to set forth the merits or defects of particular articles, must here be futile. Such a universe of materials, inventions and fabrics defies that mode of treatment. But I will endeavor to give some general idea of the Exhibition.

If you enter the building at the East, you are in the midst of the American contributions, to which a great space has been allotted, which they meagerly fill. Passing westward down the aisle, our next neighbor is Russia, who had not an eighth of our space allotted to her, and has filled that little far less thoroughly and creditably than we have. It is said that the greater part of the Russian articles intended for the Fair are yet ice-bound in the Baltic. France, Austria, Switzerland, Prussia and other German States succeed her; the French contributions being equal (I think) in value, if not in extent and variety, to those of all the rest of the Continent. Bohemia has sent some admirable Glassware; Austria a suit of apartments thoroughly and sumptuously furnished, which wins much regard and some admiration. There is of course a great array of tasteful design and exquisite workmanship from France, though I do not just now call to mind any article of transcendent merit.

The main aisle is very wide, forming a broad promenade on each side with a collection of Sculpture, Statuary, Casts, &c. &c. between them. Foremost among these is Powers's Greek Slave, never seen to better advantage; and I should say there are from fifty to a hundred other works of Art—mainly in Marble or Bronze.—Some of them have great merit. Having passed down this avenue several hundred Feet, you reach the Transept, where the great diamond "Koh-i-Noor" (Mountain of Light) with other royal contributions, have place. Here, in the exact center of the Exhibition, is a beautiful Fountain (nearly all glass but the water,) which has rarely been excelled in design or effect. The fluid is projected to a height of some thirty feet, falling thence into a succession of regularly enlarging glass basins, and finally reaching in streams and spray the reservoir below. A hundred feet or more on either side stand two stately, graceful trees, entirely included in the building, whose roof of glass rises clear above them, seeming a nearer sky. These trees (elms, I believe) are fuller and fresher in leaf than those outside, having been shielded from the chilling air and warmed by the genial roof. Nature's contribution to the Great Exhibition is certainly a very admirable one, and fairly entitles her to a first-class Medal.

The other half of the main aisle is externally a duplicate of that already described, but is somewhat differently filled. This is the British end of the Exhibition, containing far more in quantity than all the rest put together. The finest and costliest fabrics are ranged on either side of this end of the grand aisle.

The show of Colonial products is not vast but comprehensive, giving a vivid idea of the wide extent and various climates of Britain's dependencies. Corn, Wheat, &c., from the Canadas; Sugar and Coffee from the West Indies; fine Wood from Australia; Rice, Cotton, &c., from India; with the diversified products of Asia, Africa and America, fill this department. Manufactured textile fabrics from Sydney, from India, and from Upper Canada, are here very near each other; while Minerals, Woods, &c., from every land and every clime are nearly in contact. I apprehend John Bull, whatever else he may learn, will not be taught meekness by this Exhibition.

The Mineral department of the British display is situated on the south side. I think it can hardly be less than five hundred feet long by over one hundred wide, and it is doubtless the most complete ever thus set before the public. Here are shown every variety and condition of Coal, and of Iron, Copper, Lead, Tin, &c. Of Gold there is little, and of Silver, Zinc, Quicksilver, &c., not a great deal. But not only are the Ores of the metals first named varied and abundant, with Native Copper, Silver, &c., but the metals are also shown in every stage of their progress, from the rude elements just wrenched from the earth to the most refined and perfect bars or ingots. This department will richly reward the study of the mineralogists, present and future.

Directly opposite, on the North side of the British half of the main avenue, is the British exhibition of Machinery, occupying even more space than the Minerals. I never saw one-fourth as much Machinery together before; I do not expect ever to see so much again. Almost every thing that a Briton has ever invented, improved or patented in the way of Machinery is here brought together. The great Cylinder Press on which The Times is printed (not the individual, but the kind) may here be seen in operation; the cylinders revolve horizontally as ours do vertically; and though something is gained in security by the British press, more must be lost in speed. Hoe's last has not yet been equaled on this island. But in Spinning, Weaving, and the subsidiary arts there are some things here, to me novelties, which our manufacturers must borrow or surpass; though I doubt whether spinning, on the whole, is effected with less labor in Great Britain than in the United States. There are many recent improvements here, but I observe none of absorbing interest. However, I have much yet to see and more to comprehend in this department. I saw one loom weaving Lace of a width which seemed at least three yards; a Pump that would throw very nearly water enough to run a grist-mill, &c. &c. I think the American genius is quicker, more wide-awake, more fertile than the British; I think that if our manufactures were as extensive and firmly established as the British, we should invent and improve machinery much faster than they do; but I do not wish to deny that this is quite a considerable country.

Wednesday, May 7—4 P. M.

I have just returned from another and my seventh daily visit to the Great Exhibition. I believe I have thus far been among the most industrious visitors, and yet I have not yet even glanced at one-half the articles exhibited, while I have only glanced at most of those I have seen. Of course, I am in no condition to pronounce judgments, and any opinion I may express must be taken subject to future revisal and modification.

I know well that so large and diversified a show of Machinery could not be made up in the United States as is here presented in behalf of British Invention; yet I think a strictly American Fair might be got up which would evince more originality of creation or design. If I am wrong in this, I shall cheerfully say so when convinced of it. Many of these machines are very good of their kind without involving any novel principle or important adaptation. With regard to Flax-Dressing, for example, I find less here than I had hoped to see; and though what I have seen appears to do its work well and with commendable economy of material, I think there are more efficient and rapid Flax-Dressers in the United States than are contained in this Exhibition. I have not yet examined the machinery for Spinning and Weaving the dressed Flax fiber, but am glad to see that it is in operation. The report that the experiments in Flax-Cotton have "failed" does not in the least discourage me. Who ever heard of a great economical discovery or invention that had not been repeatedly pronounced a failure before it ultimately and indubitably succeeded?

I found one promising invention in the British department to-day, viz: Henley's Magnetic Telegraph, or rather, the generator of its power. The magnet, I was assured, did not require nor consume any substance whatever, but generated its electricity spontaneously, and in equal measure in all varieties of weather, so that the wildest storm of lightning, hail, snow or rain makes no difference in the working of the Telegraph. If such be the fact, the invention is one of great merit and value, and must be speedily adopted in our country, where the liability of Telegraphs to be interrupted by storms is a crying evil. I trust it is now near its end.

Switzerland has a very fine show of Fabrics in the Fair—I think more in proportion to her numbers than any other Foreign Nation. Of Silks she displays a great amount, and they are mainly of excellent quality. She shows Shawls, Ginghams, Woolens, &c., beside, as well as Watches and Jewelry; but her Silk is her best point. The Chinese, Australian, Egyptian and Mexican contributions are quite interesting, but they suggest little or nothing, unless it be the stolidity of their contrivers.

I see that Punch this week reiterates The Times's slurs at the meagerness and poverty of the American contribution. This is meanly invidious and undeserved. The inventors, artisans and other producers of our Country who did not see fit to incur the heavy expense of sending their most valuable products to a fair held three to five thousand miles away are unaffected by this studied disparagement, and those who have sent certainly do not deserve it. They are in no manner responsible for the setting apart for American contributions of more space than they fill; they have rather deserved consideration and kind treatment on the part of the London Press. Beside, the value of their contributions is not at all gauged by the space they fill nor by the impression they make on the wondering gaze; articles of great merit and utility often making no figure at all compared with a case of figured silks or mantel ornaments which answer no purpose here but the owner's. And when it is considered that the manufacturers of France, Germany and Switzerland, as well as England, are here displaying their wares and fabrics before the eyes of thousands and tens of thousands of their customers—that their cases in the Crystal Palace are in fact so many gigantic advertisements, read and admired by myriads of merchants and other buyers from all parts of the world, the unfairness of the comparison instituted by the London Press becomes apparent. Our exhibitors can derive no such advantage from the Fair—certainly not to any such extent. The "Bay State Mills," for example, has a good display of Shawls here, hardly surpassed, considering quality and price, by any other; yet nobody but Americans will thereby be tempted to give them orders; while a British, Scotch, French or Swiss shawl-manufacturer exhibiting just such a case, is morally certain of gaining customers thereby in all parts of the world. But enough on this head.

I may add that many Americans have been deterred from sending by an impression that nothing would be admitted that was not sent out in the St. Lawrence, or at all events unless received early in April. But articles are still acceptable, at least in our department; and I venture to say that any invention, model, machine or fabric of decided merit which may reach our Commissioner free of charge before the end of June will have a place assigned it, although it will probably be too late to have a chance for the prizes.

These are to be mainly Medals of the finest Bronze, to cost $25, $12 and $5 respectively. Probably about one thousand of the first class, two thousand of the second and five thousand of the third will be distributed. But they are not to be given for different grades of excellence in the same field of exertion, but for radically diverse merits. The first class will be mainly if not wholly given for Inventions, Discoveries or Original Designs of rare excellence; the second class for novel applications or combinations of principles already known so as to produce articles of signal utility, cheapness or beauty; the third class will be given for decided excellence of quality or workmanship without regard to originality. By this course, it is hoped that personal heart-burnings and invidious rivalries among exhibitors may to a great extent be avoided.

I cannot close without a word of acknowledgment to our Embassador, Hon. Abbott Lawrence, for the interest he has taken and the labor he has cheerfully performed in order that our Country should be creditably represented in this Exhibition. For many months, the entire burthen of correspondence, &c., fell on his shoulders; and I doubt whether the Fair will have cost him less than five thousand dollars when it closes. That he has exerted himself in every way in behalf of his countrymen attending the Exhibition is no more than all who knew him anticipated; and his convenient location, his wide acquaintance and marked popularity here have enabled him to do a great deal. Every American voice is loud in his praise.

I walked through a good part of the galleries of the Crystal Palace this morning, with attention divided between the costly and dazzling wares and fabrics around me and the grand panorama below. Ten thousand men and women were moving from case to case, from one theme of admiration to another, in that magnificent temple of Art, so vast in its proportions that these thousands no where crowded or jostled each other; and as many more might have gazed and enjoyed in like manner without incommoding these in the least. And these added thousands will come, when the Palace, which is still a laboratory or workshop, shall have become what it aims to be, and when the charge for daily admission shall have been still farther reduced from five shillings (sterling) to one. Then will the artisans, the cultivators, the laborers, not of London only, but to a considerable extent of Great Britain, flock hither by tens of thousands to gaze on this marvellous achievement of Human Genius, Skill, Taste, and Industry, and be strengthened in heart and hope by its contemplation. And as they observe and rejoice over these trophies of Labor's might and beneficence, shall they not also perceive foreshadowed here that fairer, grander, gladder Future for them and theirs, whereof this show is a prelude and a prediction—wherein Labor shall build, replenish and adorn mansions as stately, as graceful, as commodious as this, not for others' delight and wonder, but for its own use and enjoyment—for the life-long homes of the builders, their wives and their children, who shall find within its walls not Subsistence merely, but Education, Refinement, Mental Culture, Employment and seasonable Pastime as well? Such is the vista which this edifice with its contents opens and brightens before me. Heaven hasten the day when it shall be no longer a prospect but a benignant and sure realization!