. Electric railways; a treatise on the modern development of electric traction, including practical instruction in the latest approved methods of electric equipment and operation . ime that a continuous rail would l)e an impossibility becauseof the contraction ami expansion of the rail under heat and cold,which, it was thought, would tend to pull the rails apart in coldweather and to cause them to bend and buckle out of line in hotweather. Experience has conclusively shown, however, that con-traction and expansion are not to be feared when the track is laidin a street where it is covered with
. Electric railways; a treatise on the modern development of electric traction, including practical instruction in the latest approved methods of electric equipment and operation . ime that a continuous rail would l)e an impossibility becauseof the contraction ami expansion of the rail under heat and cold,which, it was thought, would tend to pull the rails apart in coldweather and to cause them to bend and buckle out of line in hotweather. Experience has conclusively shown, however, that con-traction and expansion are not to be feared when the track is laidin a street where it is covered with paving material or dirt. Thepaving tends to hold the track in line, and to protect it from extremesof heat and cold. The reason that contraction and expansion donot work havoc on track with welded joints, is probably that therails have enough elasticity to provide for the contraction and expan-sion without breaking. It is found that the best results are secured by welding railjoints during cool weather, so that the effect of contraction in thecoldest weather will be niininuuu. In this case, of course, therewill be consideral)le expansion of the track in the hottest weather,. en < < H UH b O H o nhju I HU) < U o b< O P-. UU« <; HCCO UBRARY Of THE jNIVERSffY of lUiN^ ELECTRIC RAILWAYS 87 but this does not cause serious bending of the rails; whereas occa-sionally, if the track is welded in very hot weather, the contractionin winter will cause the joint to break. Cast=Welded Joints. The process of cast-welding joints con-sists in pouring very hot cast iron into a mould placed around theends of the rails. These moulds are of iron; and to prevent theirsticking to the joint when it is cast, they are painted inside witha mixture of linseed oil and graphite. Iron is usually poured sohot that, before it cools, the base of the rail in the center of the moltenjoint becomes partially melted, thus causing a true union of the steelrail and cast-iron joint. This makes the joint
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