The London Engineer has a long article showing the fallacy of eng meers and exptrts in condemning new improvements. The article consists in a sum mary of recent improvements which were pronounced impracticable by the engineering profession when they were first proposed, but which are now in suc cessful operation. We make the following extracts:- IRON PLATE BRIDGES. How reasonable it appearea to many, at one time less than twenty years ago-that plate iron bridges would crumple up like pasteboard

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... or leather. Possi bly there may be those, here and there, who remain still unconvinced, just as there are those who still refuse to believe in the strength and staunchness of iron ships. How many, engineers there were who could not admit that cylinder foundations could be got in by simple atmospheric pressure; and the'6 were others recently, who doubted that a disc pile could ever reach a strong footing in sand by pump ng a stream of water through it and out at the oot tom. How confidently, too, do engineers now employ concrete in numberless situations where once only stone and deep piling would have been considered secure. IRON AND STEEL MANUFACTURE. The changes which have heen brought about, with in the past few years, in the manufacture and work ing of iron and steel, are something almost incredi ble, It would have been reckoned sheer folly had engineers, evpn ten years ago, counted upon the general introduction of steel for railway axles and tyres; and steel rails were hardly known even three years ago. Krupp'S immense :ngots were, perhaps, amongst the greatest wonders of the International Exhihition-at least to minds capable ot' compre hending them; but it is likely that Bessemer's grand discovery --already brought by untiring energy and ready ingenuity to the rank of a large and rapidly growing manufacture, will work the greatest chauge in our applications of iron. Opinion has already been turned by it from unbplief into a confidence surer than any admiration however great. Even in iron making by other processes, including the ordinary course of puddling, re·heating, and rolling, the pro gress in respect of the magnitude of the pieces wrought has betn very great. It would have been seriously doubted, five or six years ago, whether armour plates a foot thick, ll,nd weighing each 2 0 tuns, could ever be mada. McHaffie's malleable cast ings up to two or three tuns weight represent a great step also beyond anything known two or three years ago. This branch of manufacture has been greatly promoted by the improvement in crucPlles, those ot plumbago now withstanding sometimes a week's work in malleable iron making, and from sixty to ninety rounds in other casting where one or two, or three, © 1865 SCIENTIFIC AMERICAN, INC. ployed. Self-stripping cards are common now whpre, ten years ago, both breakers and finishers were al ways stripped by hand. Mes�rs. Hetherington's sElf acting mule, too, bas hardly one-ha:f the parts, if indeed as many, as were originally embodied in Ricbard Roberts' great invention. Cotton spinners are notoriously jetl lous of revolutionary mechanical devices, yet the old mules are being superseded. ' A great change, too, has been wrought by the Black burn "slasher," which, within a small space, doea almost ten-rold the work of the old dressing frames. Mr. Bullough's and Mr. Taylor's inventions, too, are working their way into the weaving sheds of Lan cashire. The beautiful operation of "gassing', the yarn-an invention of the iate Mr. Samuel Hall, of surface condensing notoriety-is almost too old to be instanced in this list, but, palpaole as were the adv'antages, there Wtlre prejudices to be overcome. BREWING. The brew ere were resolute in their opposition to any invasion o{ the mysteries of thei� craft. They knew that many a vat of ale had gone off in a thunderstorm, and they argued that the damage was due to electricity, and galvanism, they though, must be the twin sister of the subtle fluid. So they would oot permit of any conjunction of iron and brass in the fermenting tuns or in the cleansing rounds. Noth ing but gun metal pumps and wooden vessels would answer. It is odd that they even permitted iron hoops upon kilderkins and barrels intend<ld to be tapped with bras, cocks. It was nothing that more t:Jan one chemist had passed currents of electricity through barrels of beer, and, although he might have decom posed a little ot the genflrous liquid, it was none the woroe for the experiment. Now the brewers have �nashing machines, attemperators, cast iron boiling ba cks, ani even slate fermenting squares-yes, slate. And there are centrifugal pumps and india rubber ho'e, yeast pre"ses, and one or two enterprising brewers have tried hop digesters, hop Reparators, and spent hop presses-with what result we will not undertake to say; but it is evident that the brewHs, interested, like other people, in rna ing money, are ro longer jealous of anything that promises a real improvement. So it is with the sugar refiners, and !!o also with the mil:erd. But for a few formidable patents in their way, the latter would all be using decorticators, ventilated millstones, and stive rooms, and grinding, perhaps, twelve or fifteen hushels of wheat per pa'r of stones per hour. It is in the success of what was at first believed to be ;'!oubtful or impracticable, that engineers gam confidence, and although the fact remains that many so-called inventions are really impracticable, or use less from other reasons, it does not the less follow that many new things which men of narrow yiews and scanty knowledge may believe to be impractica ble, are nevertheless but waiting their time of suc cess. RECENT AMERICAN PATENTS. The following are some of the most important im provements tor which L�ttRrs Patent were issued from the United States Patent Office last week; the claims may be fbund in the official list:-Compos�tion for Enameling, ,iI1etal, Wood and other Swfac es.-This inven:ion relates to a composi tion, the chief ingredients of I"hich are carbonate of lime and silicil! acid, together with such othr.r chem icals which assist in the formation of an insoluble silicate, in such manller that oy the application of said ingredients to metal, stone, or other surfaces, an enamel is formed which is capablf1 of r�sisting the influence of heat and of water, oils and most acids.