According to our promise ot last week, we have given, in the present number of the Scientific American, a more extended account of the various objects on exhibition at the Fair. For the better convenience of reference, these are classified under separate heads, so that our readers may be able to discern at a glance those subjects that are more particularly interesting to themselves. RAILROADS. Under this head are placed those inventions that have reference to locomotive travelling, and two divisions of it are particularly rich in new inventions, namely, that for the purpose of Ventilation, and that which we have assigned to Biakes. Ventilation of Railroad Cars.—Here we have two leading principles by which most of the inventors appear to have been actuated —either of admitting the air by the top or else by the under-side of the car; we shall, however, give a description of each invention separately, and leave it to the Judges to decide to whom the premium is due—" Palmam qui meruitferat." Mr. Paine was there, of course, with his ventilating apparatus, but as his plan has already been fully described and illustrated by us on page 244, Vol. 7, it will be unnecessary to say anything further upon the subject. A. R. Church, of Dansville, Ohio,obtains his mode of ventilation by means of a large pipe placed on the top of the car with a funnel at the end to catch the wind. A small pipe connected with the above is carried round the outside of each window with an open groove in the centre; this latter, by giving a vent for the wind, causes a current of air that prevents the dust from blowing into the car, acting in fact as a counter-current. In Daniel Flynn's arrangement, underneath the car is fixed a refrigerator filled with ice or water, which purifies the air above intended for ventilation, there being between the floor of the car and the refrigerator a false bottom. At the top of the refrigerator are two self-acting valves, one of which is closed when the other is open. By this means fresh air is supplied to the car, from underneath the flooring, through apertures iurnished with registers to moderate the current at pleasure. The foul air is driven out by the windows and thus pre-*nts tne entrance of dust. In case the windows are shut, there is a series of self-acting valves above which answer the same purpose, and which can be severally closed by a handle inside, at the option of each passenger. Mr. Jeffrey's invention consists in a long flexible tube, running the whole length of the train from the fire-box of the locomotive, with branch pipes let into the top of each car, the commencement of the pipe near the engineer being funnel-shaped, so that the air can easily rush' in. There is one objection to this plan which struck us particularly, and for which we do not recollect to have seen any remedy : should the engine be pushing the train, instead of drawing it, the apparatus would oi course be of no avail. The plan of W. Atwood, of Waterbury, Ct., consists of a rectangular frame-work placed before the door of each car, of a larger size than the latter, and made, apparently, of textile india rubber. It will thus be seen that when two cars are coupled the?? india rubber framing of both, which is shaped lilfe a bellows, closely approach each other, and prevent the admission of the dust, while the air can pass through. Clinton Roosevelt has a plan which consists of a fan and bellows on the top of the car, one at each end, which are driven by bands connected to the wheels, the one for rapid and the other for slow motion. Another invention of the same party consists in obtaining the necessary ventilation by fixing at the ends of the car a frame-work of buck-skin leather, which is sufficiently porous to allow the air to pass through, and yet can exclude the dust. This latter point i-s almost as great a desideratum as the ventilator, for no one travelling much on railroads can fail to find the dust an intolerable nuisance. J. C. Symmes, of West. Troy, N. Y., presents a car with a gable-shaped roof, forming an air vessel at the top of the carriage; a rectangular funnel at one end, and a species of shutter-blind at the other, complete the arrangement. As we are on the subject of ventilation, we may as well, in this place, make reference to Robinson's Ship Ventilator, which is also on exhibition, but which we do not consider valuable in every instance, especially where foul air has feeeii permitted to accumulate in the holds of ships. For ordinary purposes it may, perhaps, be ot use, but we do not think that it would1 be found effectual in ail eases. Railroad 'Brakes-—TheBrakeswhich wesaw. —and thggjut lyjiiwjHimiMng'jfeJtttoae iuiportiBflrpaiScular, viz.—originality; they are nearly all similar in the main principle to the brake in common use. In fact they nearly all act on the system of forcing a segment of a ring of wood or iron against the periphery of the wheel, which, it is well known, is far from being a new idea. The system of levers, by which such a result is effected, is a mere secondary consideration, and combinations of them may be made ad infinitum, without entitling the contrivers to the honorable name of an inventor. We may be asked, " What then would you have?" We reply, " Some, thing of which nobody has hitherto thought," —and that is what we call an invention. But to return to a description of the articles betore us, something original we have in Jackson's long action brake, in which, discarding the idea of friction against the wheel, he applies the pressure against the rail by means of a long bar extending nearly the whole length between the axles of the car. This is raised or forced down by levers. There are objections to this plan, one of which is, that it might have a tendency towards throwing the cars off the rail. Hand and Steam Brake—.By T. Walker, of New York.—This invention consists in applying the brake blocks to each side of each wheel, thereby more effectually equalizing the strain on the axles and wheels. In order to be worked either by hand or steam, the brake is fitted with an apparatus by which each car can be stopped by hand without interfering with the action of ths steam on the brakes, thus rendering the. steam and hand-breaking power independent of each other. Henry Olds, of New Haven, Ct., exhibits a brake, intended to exert against the wheel more or less pressure, as required, which is effected by forming the brake in the shape of the letter C, and suspending it from a joint, not exactly in the middle of the arc, so that more or less of the periphery of the wheel is subjected to the pressure of the brake as required. The patentee has connected with this :rake a mode of ventilating cars, expecting the wheel to act as a fan in drawing off the air, whilst fresh air is admitted from the bottom, passing through a layer of sponge to deprive it of dust, c. A. A. Church, of Painesville, Ohio,' effects the application of the brake*by the operation of two men stationed in front of the engineer, who let fall a friction wheel on the track by means of a lever, and which winds up a chain connected by rods to the brake. The brake consists of slides which press upon the rail when it is required to stop the trah. Car Wheel—By H. Gardiner, of Schoharie, N. Y.—This is a good strong wheel, with wrought-iron spokes, but we observed nothing new about it. Railroad Car Seat—By A. B. Buell, of Westmoreland, Oneida Co., N. Y.— (See page 305, Vol. 7). The nature of this improvement consists in attaching to the backs of the ordinary car seats outer sliding backs, which may be raissd or lowered as required. By this means there is obtained a very compact car seat, with a back equal to a concaved high-backed chair, and it is so arranged that two persons sitting on the same seat, who may choose to have the backs at different elevations, can be accommodated to their heart's desire. W. Warren, of Cincinnati, Ohio, exhibits two new seats, which, for convenience, change of form, and adaptation to different postures, are superior to anything that we have hitherto seen. Guard Cars—By Booth Ripley, of Troy, N. Y.—This is an elaborate contrivance to receive the first shock of anything on the road, and consists of a huge clumsy-looking iron car stationed in front of the train. We also noticed two passenger cars of sheet-iron, which have the advantage of extreme lightness—one by Thomas E. Warren, of New York, illustrated and described on page 388, Vol. 6, Scientific American; the other by M. C. Butler, of New York. The fearful accidents which occur from cars running off the track or the breaking of an axle, has caused several contrivances to prevent this danger. Wm. Gee, of 66 Gold st., NV'Y,, has a pencil sketch of an invention of this kind, and has affixed letters of reference withit,but has neglected to give the correspond, ing explanation; so far, however, as we can understand his drawing, he proposes to form the wheel with a recess of large diameter, into which he fits a strong circular plate, having a box working loosely on the axle, and enabling it to be clamped to the framing; a strong plate is screwed against the inner side of the wheel to keep the whole secure. Should the axle break it is evident that the wheel will be retained in its place. A. L. Finch, of New Haven, Conn., has a plan with a similar intention; he encloses the wheel in a sort of frame, which, of course, would be similarly effectual. Station Indicator.—By M. F. Potter, of Charlemonnt, Massachusetts.—The owner of this invention is not so ambitious in his aspirations, he aims only at benevolently preventing unlucky or heedless passengers from being carried beyond their destination. For this purpose he has a species of scale inscribed with the names of the various stations on the road, and a variety of other information. This scale is suspended near the roof of the cart and when a station is approached, the name on the scale is brought forward; when the station is passed, the name is rolled up out of sight, and the next place brought under notice. The operation is effected by means of toothed wheels set in motion by the axle. We fear that the slip of the wheel is liable to deteriorate from its efficiency. Engine and Car Truck—By Edwin Stanley.—This truck, in addition to the usual advantages, is also intended to act as a relief to axles and outside rails at curves, as well as a brake, which is thus effected :—the truck has independent bearings or springs and also a guarded lateral motion, allowing the flanges of the running wheels to only touch the outside rails. ,- Selfdirecting Railroad Cars—By Lander Harding.—The principje embraced in this invention is, first, an independent motion to :he opposite wheels, by means of separate axles; second, the bringing the axles into the line of the radii of the curve, thereby causing the wheels to follow the same on a curved or straight road. Compound Car Axle—By P. G. Gardiner, of New York.—This appears to be an ingenious invention to overcome the difficulty which occurs from the wheels being keyed on to the axle. It is obvious that when traversing a curve, the wheel on the rails'which has the smallest radius requires to move at a less velocity than the other. The impossibility of doing this is a fruitful source of accidents, but is obviated by this plan. An axle box, somewhat similar to that used for wagons, is placed on the axle, and on this box the wheel is secured. The axle box is held in its place by a V-shaped collar, a rim of metal to correspond with the inner edge of the V is screwed on to the box, which can thus be made to act as a species of friction clutch. In ordinary cases the axle itself will revolve, but should a sudden strain occur in a curve, the axle box will work loose, and the wheel thus be enabled to acquire the diminished velocity required. Self-adjusting Railroad Simtch—By R. H. Middleton, of New York.—The right or the left wheel of the car, according to which line of rails it is upon, on approaching the switch, acts upon a short lever, so arranged that the wheel, in passing presses it down, and thus the switch is adjusted to receive the train. STEAM MACHINERY. The steam engine and its numerous appendages attract the lively curiosity of visitors, whilst the boilers give a practical illustration of the mode of setting recommended by Dr. Griffin. Stillman's Gauges are attached, as they usually are, to all well-managed'boilers, and we noticed a neatly-made counter fixed to the engine, which was rapidly numbering its quick strokes. We are glad to see this excellent little invention of James Watt brought forward for the use of land engines, and regret the omission of an Indicator. Sloan Leg-gatt's Hydrostat is attached to the Boiler, and gives ample proof of its efficiency in re-guIatmg'Be'auj.i'pl/trfjBmiMwtefy Mr. Morris, of Duane street, N. Y., has a model of an engine with two oscillating cylinders inclined at an angle to each other. The idea is somewhat similar to that of the original engines of the Great Britain, designed by Brunei, with the exception that the latter were fixed. Boardman's Boiler—The inventor proposes to supplant the common locomotive boiler by his plan, but it seems to us that the vertical position of the tubes is a great drawback. There is doubtless an enormous sacrifice of fuel in locomotive boilers, but railway companies are willing to suffer that loss to attain a high rate of speed. If the tubes according to the model, are to be fixed vertically, we doubt their superiority for a rapid generation of steam. For stationary purposes, where economy of fuel is an important object, this may probably be a desideratum. E. Gould, of Newark, N. J., D. M. Saun-ders, of Hopkinton, R. I., and others, exhibit some excellent machinists' tools. Baldwin Cunningham, of Nashua, N. H., exhibit an excellent machine for boring locomotive cylinders without the necessity of removing the cylinder from its place. All locomotive managers will be aware of the utility of this invention. Ingersoll exhibits a useful Drill Brace, in the mode of working somewhat similar to the ratchet brace, but with the advantage of moving the drill during the back stroke. Steam Paddle—By Carpenter, of Flushing, L. I.—The float blades are here made to feather by rods which slide upon an elliptical frame. The main objection to all these plans ot adjustable paddles, is the liabilityto get out of repair, otherwise they are far superior to the common paddle. Rotary Pendulum Governor—By J. Trem-per, of Buffalo, N. Y.—We noticed this governor revolving at a tremendous rate, but the fans which the maker has attached to the cylinder, make it rather embarrassing to discern. It is a modification of the ordinary governor, but must evidently be much cheaper how far it is moie efficacious we are unable to say. The many joints which are necessary to the latter, are here superseded by a cord or catgut. Judson's Governor Valve—This valve is very similar to a disc valve or to the regulator which is used in many locomotives. MISCELLANEOUS. Under this head we have comprised a variety of inventions that are not sufficiently numerous, or of sufficient importance, to be classified alone. Lightning Conductors—By Otis Streeter. —This invention consists of metal rods running down the sides of the building from which they are insulated by glass stays. Along the ridge of the roof is a horizontal rod, which connects the longitudinal conductors, and at intervals project pointed rods. Mortising Machine—By 0. Judson, of Steu-ben Co., N. Y.—This is very good for what it is intended, viz., ior piercing holes in hubs. Card Printing Press—By G. P. Gordon, of New York.—This was the only press we noticed at the Fair, at which we are rather surprized, as several patents have lately been taken out. It bids fair to become a formidable rival to the Yankee Card Press now generally used. Mr. Gordon has substituted the revolving type cylinder for the common method, —the paper is in an endless roll, and is fed down from overhead on to a flat bed, where it receives the impression from the cylinder as it revolves, and thence descending, is cut into cards as fast as printed. Paper Cutting Machine—By S. Perry.—The top cutter is fixed, and the under one revolves —as the latter approaches the paper it closes a catch above, which grips the paper so as to hold it square whilst being cut. As the lower cutter revolves, the catch or nipper is loosened, and the paper is fed down as before. Daguerreotype Suffer—By Duryea, of Wil-liamsburgh, L. I.—Here we have a new species of buffer, different from any other in use, the inventor using a straight motion instead of a circular one. A bed, covered with buff leather, is made to work to and fro by the usual foot motion. The plates are held up to the under-side of the buffer by means of a lever which the operator holds to regulate, the pressure. Street and Rail Truck Sweeper—By A. S. Watson, of Staten Island.—More likely to be used for the former purpose than tor the latter, —consisting of an apparatus fixed beneath the car. Two large geared wheels are worked by a piston ; around their edge are fixed vertical brooms, which are kept downwards by spiral springs. The pinion is worked by a species of tread-wheel mounted on the car, but we see no reason for it, as the motion of the car would be quite sufficient from which to derive power. Stone Picking Machine—By J. T. Foster, f)i Jersey City.—This invention consists of a KMt,f revolving prongs, which catch up the tiWttd jerk them into a spout, from which they afllards run into the car. It is adapted either for roads or agricultural purposes. Coupling for Shafting—By Vanzile, of New York.—The circumference of the fixed pulley is divided ifiiso segments, which are capable of expanding when acted upon by a contrivance that is moved to and fro by a long lever. Supposing the loose pulley in its place in the fixed one, by pushing the lever to the right the segments are forced out and grasp the loose pulley, which carries the shafting around with it. The weight of the lever maintains the tension of the segments. There are a few standing, embossing and oth-sr varieties of presses, in which we noticed nothing particularly new, with the exception of a standing press, (marked in the catalogue No. 1839), in which the maker has placed the screw on a horizontal instead of the usual vertical position, and has also employed an elbow-joint. There are on exhibition several of Dick's Anti-friction Presses, but most of our readers are acquainted with their excellence, having been fully described and illustrated in the Scientific American. Cotton Spinning Machine—By Brundred, of , Oldham, near Paterson, N. J. (See page 361 S Vol. 7.) —This is decidedly the best machine of the kind in use. It is of the throstle description, but no throstle will produce the fine work of which a mule is capable. However, those who desire to produce the description of thread that the throstle is capable of producing, may use this machine with advantage. Among the minor inventions are a Balance Window Sash and several Bread, Meat, and Fruit Cutters; of these latter it may be observed, that howe-v er excellent for particular purposes, they will never supersede the common knife, and the living lever by which it is worked. Bridges—Of this class we have three different inventiots—two trussed bridges and a plan of a submerged bridge for railroad purposes. The peculiarity ot the first is its lightness, too much so, in our opinion, to be compatible with bearing much weight; of the second is its strength, in proof of which the inventor, Gralley, of Brooklyn, has loaded the model, on the top, with 2:000 lbs. weight of iron, presuming, we suppose, that the actual bridge will support a proportional burthen; but theory, in such cases, is otten at variance with practice. The third, as mentioned above, is a plan of a submerged bridge for railroad purposes. The bridge, when not required for the passage of a train, is sunk at the bottom of the river, and pulled up when a train requires to pass. The idea is good, but the question is as to its general practicability; we foresee many obstacles where the river is wide'or deep, in the facility of its construction and management. Otherwise, it would be a great desideratum where stationary bridges are not allowed to be carried over rivers. AGRICULTURAL IMPLEMENTS. In this department there is on exhibition the ordinary* run of agricultural machinery, but we did not observe anything very novel in their arrangement. There are three or four different kinds of reaping and mowing machines, but there is nothing very interesting about them. The same remark is applicable to the other kinds of implements, which do not vary particularly one from the other in the arrangment of their machinery. Among the articles stationed in this part of the exhibition, we noticed a new faucet for water and other liquids, the invention of E. Stebbins, of _ghicopee, Mass. It substitutes a flat.valve, which IS raised by—arserewj-rbrthe ordinary tap ; a leather seating is used for the valve, and likewise leather packing for the screw. Abraham's patent, in England, is very similar, but probably more expensive, as he employs a mitre valve. Four Grain Cradle—By S. Wilkinson, of Middleton, Orange Co., N. Y.—This instrument differs somewhat from the ordinary cra-i dies, in the number and arrangement of its adjusting screws, as also in the shape ot the handle, which is curved differently from what is usual. From the specimen exhibited, we should conclude it to be a superior article. FINE ARTS. In this department we noticed several beautiful specimens of workmanship and taste,—a collection of medallions, busts, c,.in what is called, by the artist, Sitter—Parian composition resembling alabaster; bronze figures, c, Lucet;—with a variety of objects of luxury and use, which it would be impossible to particularize. Furniture of every description —chairs, bedsteads of iron and wood, silver ware, clock stands, telescopes, c. Fire-proof sales, so ornamented that they appeared more fit for a lady's boudoir than a merchant's counting-house. Specimens of inlaying in wood, by Volkert, Elm street, N. Y.; Electrotype specimens by John Evans, Jr. ; pictures; prints, needle-work,—and a host of miscellaneous articles. Daguerreotypes—This department of the Fair is generally very attractive to the idlers, who love to while away the time by studying tb%frious specimens of the " human face di-vjjiil' We have, as usual, a goodly collec-1 tion. Gurney exhibits below, in the body of 1 the building, some choice specimens of the art, i —there is a softness about his pictures which 1 we meet with nowhere else ; whether it arises from a more judicious light, or better pre-f {fared plates, we know not, but such is the , case. The majority of the Daguerreotypistsj s however, exhibit in the upper gallery, am here we pass, in rotation, Holmes, Meade. Root, c, c. Meade's collection has an imposing appearance from the number of extra mammoth-sized pictures exhibited, they are mostly superior specimens, but should not be ticketed, as some are, with what may be call-sd certificates of character—" good wine needs no bush." We noticed one or two ticketed in this manner, " A Rembrandt," but why or wherefore we cannot tell, as to being copies )f Rembrandt's peculiar style, we decidely )bject to the assumption. Root exhibits some specimens of crayon daguerreotypes which do him infinite credit; they are a pleasing diversity from the ordinary pictures, and depict, with great effect, the more striking traits of She physiognomy. Insley also exhibits some unique specimens of the art, which, as models )f a peculiar style, are highly commendable ; the method appears to us particularly applicable for copying statues, c, of which the spe-:irrens exhibited are copies. As a matter of :ourse, there are several other exhibitors ot this class, but the above-mentioned struck us nore particularly with their excellence.