On The Testing And Strength Of Railway Materials, &C.

is usually stipulated in the specification that the whole lot may be rejected if this one , 0 r at most a second , do not stand the trial , as several English makers have found to their cost . Some of these tests are very severe : such is that required by the Austrian Soi'them Railway , according to ivhich all five-inch steel axles , when set on supports nearly 5 ft . apart , must undergo blosvs from a weight of about 7 cwt ., foiling from a lieieht of nearly 19 ft ., increased by two feet from each successive UOAV . In this ivay it

must withstand a bend of 9 in ., the operation being continued until the axle has ivithstood more than six thousand foot pounds . A lighter test is that of the Southern Railway Company , Avho require for their 4 | - in . steel axles that , Avith a distance between the supports of nearly 5 ft ., they shall withstand a bend of more than 9-fin ., under a 7 cwt . monke }' , falling from a height of nearly 15 ft . They must then allow themselves to be bent back straig ht in a same manner Avithout breaking . In fact , almost every other company ' s engineer has a different test , differing as to the distance between the

supports , the Aveight of the monkey , and the height of its fall . The texture of commercial iron varies greatly according to its mode of manufacture . Pure iron , which has been formed and rolled equally in all directions , exhibits a texture of very small brilliant grains , but Avhen drawn out into bars its texture is fibrous , the fibres always running in the direction of the bar which may be readily proved by breaking it . The fibrous texture is more tenacious than the granular , and bears a greater tensile strain

without breaking . Iron of a fibrous nature sometimes changes into the granular when subject to much "vibration , as rods in suspension bridges , & c . Its tensile power then rapidly diminishes . It is Avell known to manufacturers and to many others , that steel of the strength of 33 to 36 tons per inch can be made , and is made in large quantities at moderate prices , possessing all the toughness and malleability required in engineering structures . We

have this on the authority of Mr . W . H . Barlow , and yet engineers , as a rule in England , do not seem to take kindly to it—for bridge building at any rate—in this respect we are behind our American friends . The malleability of steel will be shown by the following test : —

A jfiece of rail Aveighing SOlb . per yard , and 12 ft . in length , Avas held by one end , and twisted at the other until it made 6 f complete revolutions before it broke . The fracture occurred at one end , leaving about lift , of the rail in the twisted form Avhich had been g iven to it . In this tivisted state the rail Avas laid on two bearings , 3 ft . Gin . apart , and subjected to the UOAVS of 1 ton Aveight falling 30 ft ., and it bore one of these bloivs without breaking . Mr . Barloiv gives the limiting span of a girder in iron at 5

tons per inch strain as 600 ft ,, and in steel at 8 tons per inch strain as 900 ft . We can obtain an idea of the effect of introducing steel by this , and Mr . Barlow says , assuming a load in addition to the Aveight of the girder of one ton to the foot , the relative weig hts under these circumstances would be : —

Weight of Steel ^ Veigll ^ . of Iron Span . girder in tons . girder hi tons 200 , 57 100 300 150 300 400 320 800 With these facts before ussurely we ought to turn our attention to this metaland

, , get the Board of Trade to state a limiting strain as they do in iron . MALLEABLE CAST IRON . In 1804 , Mr . Samual Lucas , of Sheffield , patented a mode of producing malleable cast iron , his specification clearly showing the theory of conversion , and the firm Echvard Lucas and Sonof Dronfield Foundryare still engaged in its manufacture

, , , The colour , both of external , and that of fractured specimens approach that of steel . The " malleableized " metal takes readily a very fine polish , Avhich is not easily destroyed , upon exposure to moisture . Malleable cast iron is easily stamped , clraAvn , and hammered Without heating . It can also be worked ivell under the hammer at a , IOAV heat , and at