with the Danish firm Kampsax. Kampsax at that time was active in railway construction in Turkey and the Shah followed the Turkish recommendation which had the additional advantage of bringing in a company from a small country which posed no political risk for Iranian independence. Kampsax subcontracted the project in 43 lots to companies from Europe, the USA and Iran. Kampsax engineers supervised the works on each lot, the works being coordinated from the head office in Tehran. The contract required Kampsax to complete the line by May 1939. Kampsax completed the project under-budget and ahead of schedule, with it being formally opened throughout on 26 August 1938. The first official steam locomotive conductor to ride the line was an Iranian named Hossein Orang. The first lines passed through formidable mountains. Long stretches have gradients of up to 1 in 36 and hillclimbing techniques such as railway spirals. The Three Golden Lines (Se Khat Tala) spiral is on the Mazandaran branch in the Sewatcow (Savadkuh) County of Mazanderan just a few kilometers south of Veresk Bridge. The line ascends or descends in a short distance by passing three times in the same area at different heights. Trains descend towards Sari or ascend in the opposite direction by going through the Dowgal twin tunnels. The line is 1,394 km long, has about 230 tunnels and 4100 bridges and its highest point is at Arak, 2,220 m above sea level. However, Kampsax' contractors laid relatively lightweight rails, ranging from 67 to 75 lbs per yard, that restricted the axle loads that the line could carry. Engineering and geological challenges Various geological problems were encountered, requiring abandonment of some tunnels and realignment of the route through different terrain: A tunnel through a salt dome was abandoned because the disrupted water table would erode away the salt. A tunnel started through apparently solid rock was abandoned after it encountered powdery gypsum that filled the excavation as quickly as it was dug out. A tunnel through pumice could not be blasted and could not be dug as the picks and shovels became stuck. A tunnel encountered a large "void" or cavern in the mountain that required a bridge within the tunnel. Poor fresh water supplies made mixing of long-lasting mortar and concrete problematic. Large bridges such as the Veresk Bridge were necessary to cross the Alborz mountains. Locomotives In 1936 Beyer, Peacock & Company supplied