106 REPORT — 1842. 



of 60°, with a crystalline fracture ; by raising the temperature 40° higher, it bore 

 twenty blows, and broke with the fibrous or ligneous fracture ; so that the quality 

 of iron was not the only circumstance to be considered as influencing the fracture. 

 Mr. Nasmyth noticed also the injurious effect of cold swaging, as causing a change 

 in the nature and fracture of the iron. Swaging was necessary in many cases ; 

 for instance, when an axle had collars welded on, these could not be finished with 

 the hammer alone, certain tools called swages were used, from the action of which 

 great condensation of the iron took place, and a beautiful polish was given to the 

 surface, with what injurious effect he would show by the next specimen, which had 

 been heated red-hot, and then swaged till cold ; it broke at one blow without nick- 

 iDg, and the fracture was very close and beautiful, like steel. This showed the fal- 

 lacy of considering close fine grain a good test of excellence in wrought iron ; but 

 moderate swaging was often necessary, and not injurious, unless where an over re- 

 gard to finish carried it to excess. To prove that annealing restored the toughness 

 and fibrous texture, a portion of the last bar was heated, and swaged till cold as 

 before, then heated dull red, and left to cool gradually ; it bore 105 blows without 

 breaking, as was shown by the specimen ; this proved that the fibrous structure was 

 restored by annealing, and he therefore thought it should be insisted on in specifica- 

 tions. The effect of heating to welding-heat was very injurious, unless the iron was 

 subsequently hammered to close the texture ; a piece of the same iron heated to weld- 

 ing, and left to cool, broke without nicking in one blow, showing very large crystals, 

 especially in the centre. The effect of nicking was also very singular. The strength 

 of iron was generally stated to be proportional to its sectional area ; but,a nick not 

 removing -ri-oth of the area, took away T Vth of the strength. Mr. Nasmyth broke 

 a piece of nicked, or rather scratched wire, to illustrate this point. These and similar 

 things did not prove that science and practice were at issue ; but, as Halley reached 

 the great accuracy of his prediction of the return of his comet by taking into account 

 the disturbing forces of Jupiter and Saturn, and the other planets amongst which 

 the body had to pass, so scientific men should seek in the workshops correctional 

 formulae, by learning there the practical occurrences which would elucidate and cor- 

 rect their theories. 



On the best Form of Rails and the Upper Works of Railways generally. 

 By Prof Vignoles. 



He wished to compare the two chief systems of laying down rails, with chairs 

 and without, and to do so he referred to two diagrams : — No. 1, exhibiting the 

 heavy rail and heavy chair used on the South-Eastern Railway, the weight of rail 

 being 80 lbs. per yard, and the chair 20 lbs. : the rail was fastened in the chair, not 

 with iron, but with a longitudinal plug or key of wood : this mode of laying rails 

 was found to answer very well. No. 2 was invented by Mr. Evans ; it was rolled 

 with a slot or groove running along its under side ; this slot, after coming from the 

 first rollers, was rendered dovetailed by compressing the bottom edges of the rail 

 towards each other, thereby narrowing the slot at the bottom. These rails required 

 no chairs, having continuous bearing on longitudinal wooden sleepers, being fastened 

 down by bolts, with dovetailed heads slid into the groove, and which, passing 

 through holes in the timbers, were secured with a nut and washer at the under side. 

 He had suggested this improvement, as they had been previously fastened with a 

 cotter. By this method all the difficulties attendant on fastening down the chairs 

 were removed. The chairs had been fastened with bolts and screws, but he had 

 found that on the slightest loosening the bolt-heads flew off, from the continual per- 

 cussions, and the screws very soon allowed vertical play from the yielding of the 

 fibre of the wood. By Evans's rail we secured the rail without the intervention of 

 the fibre of the wood. One inconvenience attending it was, the trouble of scraping 

 away the earth to tighten the nuts when necessary ; but this might be partially 

 remedied by placing the bolts as often as possible in the transverse gutters for drain- 

 ing the road, by which at least one-half the bolts might be easily got at; and the 

 difficulty of tightening the remaining bolts would be lessened, if, as he recom- 

 mended, the timbers were left uncovered. He preferred thus giving a free circula- 

 tion of air, and disliked burying the sleepers in ballast. The weight of Evans's rail 

 was only 45 lbs. per yard, although quite strong enough, while that of the other with 



