London, Tuesday, July 26, 1851.

If I return this once more and for the last time to the subject of American contributions to the great Exposition, it shall not be said with truth that my impulse is a feeling of soreness and chagrin. Within the last few days, a very decided and gratifying change has taken place in the current of opinion here with regard to American invention and its results. One cause of this was the late formal trial of American (with other foreign) Plows, in the presence of the Agricultural Jury; which trial, though partial and hurried, was followed by immediate orders for an American Plow then tested (Starbuck's) from Englishmen, Belgians and Frenchmen, including several Agricultural Societies. If a hundred of those Plows were here, they might be sold at once; in their absence, the full price has been paid down for some twenty or thirty, to be shipped at New-York, and be thenceforth at the risk and cost of the buyers. And these orders have just commenced. The London journals which had reporters present (some of which journals ridiculed our Farming Implements expressly a few weeks ago), now grudgingly admit that the American Plows did their work with less draft than was required by their European rivals, but add that they did not do it so well. Such was not the judgment of other witnesses of the trial, as the purchases, among other things, attest.

A still more signal triumph to American ingenuity was accorded on Thursday. Mr. Mechi, formerly a London merchant, having acquired a competence by trade, retired some years since to a farm in Essex, about forty miles off, where he is vigorously prosecuting a system of High Farming, employing the most effective implements and agencies of all kinds. He annually has a gathering of distinguished farmers and others to inspect his estate and see how his "book farming" gets on. This festival occurred day before yesterday—a sour, dark, drenching day—notwithstanding which, nearly two hundred persons were present. Among others, several machines for cutting Grain were exhibited and tested, including two (Hussey's and McCormick's) from America, and an English one which was declared on all hands a mere imitation of Hussey's. Neither the original nor the copy, however, appear to have operated to the satisfaction of the assembly, perhaps owing to the badness of the weather and its effects on the draggled, unripe grain. With McCormick's a very different result was obtained. This machine is so well known in our Wheat-growing districts that I need only remark that it is the same lately ridiculed by one of the great London journals as "a cross between an Astley's chariot, a treadmill and a flying machine," and its uncouth appearance has been a standing butt for the London reporters at the Exhibition. It was the ready exemplar of American distortion and absurdity in the domain of Art. It came into the field at Mechi's, therefore, to confront a tribunal (not the official but the popular) already prepared for its condemnation. Before it stood John Bull, burly, dogged and determined not to be humbugged—his judgment made up and his sentence ready to be recorded. Nothing disconcerted, the brown, rough, homespun Yankee in charge jumped on the box, starting the team at a smart walk, setting the blades of the machine in lively operation, and commenced raking off the grain in sheaf-piles ready for binding,—cutting a breadth of nine or ten feet cleanly and carefully as fast as a span of horses could comfortably step. There was a moment, and but a moment of suspense; human prejudice could hold out no longer; and burst after burst of involuntary cheers from the whole crowd proclaimed the triumph of the Yankee "treadmill." That triumph has since been the leading topic in all agricultural circles. The Times' report speaks of it as beyond doubt, as placing the harvest absolutely under the farmer's control, and as ensuring a complete and most auspicious revolution in the harvesting operations of this country. I would gladly give the whole account, which, grudgingly towards the inventor, but unqualifiedly as to the machine, speaks of the latter as "securing to English farming protection against climate and an economy of labor which must prove of incalculable advantage." Pretty well for "a cross between an Astley's chariot, a flying machine and a treadmill."

Mr. McCormick, I hear, is probably now on his way hither from the United States, and will be rather astonished on landing to find himself a lion. Half a dozen makers and sellers of Agricultural implements, are already on the watch for him, and if he makes his bargain wisely, he is morally sure of a fortune from England alone. His machine and its operator were the center of an eager circle to-day, and if five hundred of the former were to be had here, they would all be bought within a month. There is to be another public trial, merely to place beyond doubt its capacity to cut dry and ripe grain as well as green and wet; but those who have seen it work in the States will not care much for that.[C]

Mr. Hobbs, of the American Bank Lock Company, has had a recent trial of the Chubb Lock, so long deemed invincible here, and consumed twenty-four minutes and a half in picking it, under the supervision of judges of unquestionable ability and impartiality. He then re-locked it without disturbing the "Detector," and left it as when it was set before him. He has now to try his skill on the "Bramah" lock under the challenge for £200; and, should he be able to open it, he says he shall there rest the case.[D] He has been sent for by the Governor of the Bank of England, and will respond to the invitation. His operations have of course excited some feeling among those whose interests were affected by them; yet it is manifestly proper and important, if the locks relied on by banks and other depositories of treasure here are not secure against burglary, that the fact should be known. Unless I err as to his success at the forthcoming trial with the Bramah lock, British locksmiths must commence at once to learn their business over again under Yankee tuition.

I might give other facts in support of my judgment that our Country has not been and will not be disgraced by her share in this Exhibition, but I forbear. Had we declined altogether the invitation to participate in this show, we certainly would have been discredited in the world's opinion, however unjustly; had we attempted to rival the costly tissues, dainty carvings, rich mosaics, and innumerable gewgaws of Europe, we should have shown equal bad taste and unsound judgment, and would have deservedly been laughed at. Our real error consists, not in neglecting to send articles to rival the rich fabrics and wares of this Continent, but in sending too few of those homely but most important products in which we unquestionably lead the world. We have a good many such here now, but we should have had many more. One such plain, odd-looking concern as McCormick's Reaper, though it makes no figure in the eyes of mere sight-seers in comparison with an inlaid Table or a case of Paris Bonnets, is of more practical account than a Crystal Palace full of those, and so will ultimately be regarded. Looking to-day at Mitchell's admirable new Map of the United States and their Territories, as now existing, which worthily fills an honorable place in the Exhibition, with several but too few others of the same class, I could not but regret that a set of Harpers' Common School Libraries, with a brief account of the origin and progress of our School Library system, had not been contributed; and I wish I had myself spent fifty dollars if necessary to place in the Exhibition a good collection of American School Books. If there shall ever be another World's Exhibition, I bespeak a conspicuous place in it for a model American country School-House, with its Library, Globes, Maps, Black-Board, Class Books, &c., and a succinct account of our Common School system, printed in the five or six principal languages of Europe for gratuitous distribution to all who may apply for it. With this got up as it should be, I would not mind admitting that in Porcelain and Laces, Ormolu and Trinkets, Europe is yet several years ahead of us.

Mr. J. S. Gwynne of our State, whose "Balanced Centrifugal Pump" made a sensation and obtained a Gold Medal at our Institute Fair last October, is here with it, and proposes a public trial of its qualities in competition with the rival English pumps of Appold and Bessimer for $1,000, to be paid by the loser to the Mechanics' Society. Mr. Gwynne claims that these English Pumps (which have been among the chief attractions of the department of British Machinery) are palpable plagiarisms from his invention, and not well done at that. He, of course, does not claim the idea of a Centrifugal Pump as his own, for it is much older than any of them, but he does claim that adaptation of the idea which has rendered it effective and valuable. I am reliably informed that he has just sold his Scotch patent only for the comfortable sum of £10,000 sterling, or nearly $50,000; and this is but one of several inventions for which he has found a ready market here at liberal prices. I cite his case (for he is one of several Americans who have recently sold their European patents here at high figures) as a final answer to those who croak that our country is disgraced, and regret that any American ever came near the Exhibition. Had these discerning and patriotic gentlemen been interested in these patents, they might have taken a different view of the matter. Even my New-York friend, whose toadyism in exhibiting a capital pair of Oars inscribed "A present for the Prince of Wales," I have already characterized as it deserves, yesterday informed me that he had sold $15,000 worth of Oars here since the Fair opened. I am sure I rejoice in his good fortune, and hope it may insure the improvement of his taste also.

There are many articles in the American department of which I would gladly speak, that have attracted no public notice. Since I left for the Continent, Mrs. A. Nicholson, formerly of our city, has sent in a Table-Cover worked in Berlin Wool from the centre outward so as to form a perfect circle, or succession of circles, from centre to circumference, with a great variety of brilliant colors imperceptibly shading into each other. This having been made entirely by hand, with no implement but a common cut nail, the process is of course too slow to be valuable; but the result attained may very probably afford useful hints and suggestions to inventors of weaving machinery.—I think the display of Flint Glass by the Brooklyn Company is equal in purity and fineness to any other plain Glass in the Exhibition, and only regret that the quantity sent had not been larger. I regret far more that the "Hillotype," for giving sun-pictures with the colors of life, has not yet made its appearance here, while the "Caloric Engine" (using compressed and heated air instead of water for the generation of power), was not ready in season to justify a decision on its merits by the Jury of its Class; and so with other recent American inventions of which high hopes are entertained. We ought to have had here a show merely of Inventions, Machines and Implements exceeding the entire contents of the American Department—ought to have had, apart from any question of National credit, if only because the inventors' interests would have been subserved thereby—and we should have had much more than we actually have, had the state of the British Patent-Laws been less outrageous than it is. A patent here costs ten times as much as in the United States, and is worth little when you have it—that is, it is not even an opinion that the patentee has really invented anything, but merely an evidence that he claimed to have done so at such a date, and a permission to prove that he actually did, if he can. In other words; a patent gives a permission and an opportunity to contend legally for your rights; and if the holder is known to have money enough, it generally suffices; if not, he can and will be not only plundered with impunity, but defied and laughed at. A bill radically revising the British Patent-Laws is now on its way through Parliament, but in its absence many American inventors refused to expose themselves to a loss of their inventions by exhibiting them at the Fair; and who can blame them?

The succession of fÊtes to be given by the Municipality of Paris to the Royal Commissioners, Jurors, &c., in honor of the World's Exhibition, opens this week, and will be brilliant and gratifying as no other city but Paris could make it. The number invited is over One Thousand, and all are taken from the British shore in French National Vessels, and thenceforth will be the guests of their inviters until they shall again be landed at an English port, paying nothing themselves for travel, entertainment, balls, &c., &c. This is certainly handsome, and I acknowledge the courtesy, though I shall not accept the invitation. I leave for Scotland and Ireland on Monday.

FOOTNOTES:

[C] This trial took place at Mechi's some three weeks later, and resulted in a complete triumph for the reaper, which thereupon received an award (already accorded it by the Council of Chairmen, subject to revision upon the result of this trial), of a first-class or Great-Medal.