From Auchincloss' Report on Steam Engineering at the Paris Exposition. The rapid extension of railway interests in tropical countries, as Egypt, India, Algeria, and South America, with the | increased scarcity of timber for ties in more civilized portions | of the world, have concentrated the efforts of inventive talent toward the production of what may justly be termed a permanent road bed. The present Exposition contains some interesting signs of progress in this direction ; a few only will be selected as types, uniting simplicity of construction with practical utility. The cast-iron pot sleeper introduced on the Alexandria, Cairo, and Suez Railway, by Mr. R. Stephenson, iu the year 1851, receives the unqualified approbation of the local engineers, as best adapted to the compact sands of the Suez isthmus and the loose alluvial soil of the Nile delta. Even heavy engines running at high speeds over the Egyptian rails (which weigh 65 pounds per yard) have no serious effi'ct on these sleepers. As to the rigidity of the road-bed compared with the wooden-sleeper system, we are sure that those who have traveled the length of this route must have discovered no cause of complaint ; but, on the contrary, have admired the smooth running of the trains. This sleeper known as Griffon's patent is an oval casting (26 inches by 17 inches) having a channel along the dome-like surface for the reception of the rail; distance bars are let into cored sockets and maintain the uniformity of the gage. The Economic Permanent Way Company, of London, manufacture a hollow chair whose upper surface forms portion of a cylinder 30 inches long, the chord of the arc 13 inches, and versed sine five inches. A channel cored in the back of the casting receives the rail, which is held in place by two bolts passing through four lugs, two fixed and two movable. Distance bars regulate the gage, and the chairs are placed 44 inches between centers. The system of Mr. J. Vantlierim, of Frai-sans, is adopted on portions of the Northern Railway of France and the railway of Lyons. He submits a rolled iron sleeper for wood, and retains the rail with gibs and keys passing through wrouglit-iron clamps and the sleeper. The latter has a base of 10 inches, hight of 3f inches ; is 5 inches in width at the top and J inch in thickness. A curvature with a versed sine of 3 inches is impressed on all the sleepers, thus carrying their centers below the ballast, and by the arched form imparting greater rigidity to the beam. The Marcinelle Couillet Company, of Charleroi, Belgium, exhibit a section of railway with its wrouglit-iron ties attached, which has been in actual service during four and a half years, and gives evidence of great durability. It is worthy the attention of parties opposed to wrought-iron ties (from their want of the elasticity peculiar to wooden ones), since it forms a compromise between the two ; in which wood acts as the mere cushion ; iron the solid foundation. The rails are 4J inches deep, with 2|-inch head and 4|-inch base, the gage 4 feet 8| inches ; all the joints are formed on the j " fished principle," and secured with 4|-inch bolts. The I sleepers are simply rolled I-beams 8 feet 5 inches long (7 inches deep, -JL-inch web, and 24-4nch heads), placed 36 inches between centers. Instead of resting directly on these, a 1 painted oak block is interposed between them and the rail. Such blocks are 10 inclios long, by 6J inches wide, by 2|-inclies thick, and have a channel 4J- inches wide by J inch deep, in whicli the base of the rail rests. I'wo f-incli bolts with l|-iiich round wishers) secure the rail to the I-beam ; the latter, it should be observed, lies with its web in a horizontal position. The bolt holes are bored close to the flanges of the rails, to allow of the ?vashers clamping the latter, and the points of the bolts are slightly burred to prevent the loosening of the nut. An increase in the diameter of the washer might be made with evident advantage. The Hartwich system, introduced on the Rhnan and Cologne Railway dispenses with sleepers altogether by using very deep rails having broad bases. Their rails are rolled 9f inches deep (with Sf-mcli head, 4f-inch base, |-inch web), and the gage regulated by 1-inch rods placed six feet three inches apart, having threads on their ends and a nut on each side of the rail webs. To preserve the upper parts of these deep rails from variation, the rods pass through holes only three inches below the head, and every fourth space between rods has an intermediate one near the lower flanges of th e rails. Fish-joints give the rails the rigidity possessed by continuous beams, while the ballasting covers all except their heads. Steel rails, and iron rails with steel heads, are well represented in all the departments and produce the impression that the plain iron rail, for roads of very extensive traffic, will soon be a relic of the past. Several manufacturers show specimens of steel reversible crossings, while Austria and Holland are creditably represented by those of chilled iron. Mr. G. ?. Dering, of Loch leys, Welwyn Herts, England, exhibits samples of a tempered steel spring clip for rail joints, which appeared in the Exliibition in 1863, and has since performed good service on lines like the Great Northern, also Great Southern and Western Railways. This clip forms a steel case enveloping the extremities of the rail, and binds the same with ircreascd tcn.acity undT the pressure of heavy lo.ads. A joint constructed on this principle was carefully tested by D. Kirkaldy, Esq., and found to have a deflection of 1-31 inch under a load of 33,000 pounds, with supports 36 inches apart. AVheu the load was n-raoved the chji assumed its normal condition free of permanent set. He also tested under the same conditions two rails united by the ordinary fish-joint. Seventeen thousand pounds served to produce a deflctiun of 3 78 inch, from whi( h the joint failed to recover after tlie removal of the load. This clip is entirely free of bolts, nuts, etc., which are liable to became loose even under the closest inspection. The subject of railway plant should not be concluded without first alluding to a new spike thimble. One serious objection to soft, cheap timber for railway ties has hitherto been the liability of the spikes holding down the rails to become loosened. This results in part from the tendency of the rails to spread under the action of heavy trains running at high speed, thus crowding the spike laterally into the soft flber. Mr. Desbrire, 68 Rue de Provence, Paris, has patented a cast-iron thimble for surrounding the spike and bringing a greater number of the flbers to bear in resisting its crushing efi'ect. These thimbles are tvo inches in diameter, one and one quarter inch thick, having a three quarter-inch square or round hole cored in the center, and are sliglitly di hed on the under side, A recess one quarter inch deep is left on the upper side in which the rail rests, and prevents any tendency to its rotation. Either spikes or galvanized wood screws (three fourths inch by four and a half inches) are used for retaining the rails. Specimens of ties laid with these thimbles in April, 1862, on the Algerian Railway, near Bhdah, well illustrate the benefits to be derived. They are in use on the Northern Railway of France, at Charentes and at Mont Cenis. This principle might render important service in parts of our own country where ties of durable close-grained woods are difiicult to procure.