1918] on The Romance of Petroleum 847 



model is before jou, are with few exceptions driven by steam- 

 engines, and as a rule the steam is raised by the combustion of oil 

 fuel, but within recent years some have been built with internal- 

 combustion engines, with resulting economy in fuel consumption. 

 Of the later additions to the large fleet of such vessels, some are of 

 great size, carrying as much as 15,000 tons of oil, but the more 

 usual cargo capacity is from 5000 to 10,000 tons. 



The evolution of the tank steamer occupied many years. As 

 far back as ISlx, Ludwig Xobel, the Swedish pioneer in the 

 Russian petroleum industry, constructed the first of these vessels 

 employed on the Caspian Sea in the transport of petroleum from 

 Baku to the mouth of the Volga. At an earlier date, viz. between 

 1<S69 and 1872, a wooden ship fitted with 59 small tanks, with an 

 aggregate capacity of 794 tons, had been employed in the transport 



- |s ~ 



Fig. G. — Mesopotamia. Refinery. 



of -crude petroleum from the United States to Europe, and in the 

 latter year the first steamship was built for the carrying of oil in 

 bulk across the Atlantic, but was never used for the purpose. It was 

 not, in fact, until 1885, seven years after Nobel had demonstrated 

 the success of the system, that the first tank steamship employed in 

 the Transatlantic service was built. 



There was at first diversity of opinion among naval architects and 

 shipbuilders as to whether the oil tanks should be formed of the 

 " skin " of the ship, as shown in this model, or should be indepen- 

 dent, l)ut the former construction is now always adopted. The two 

 essential features are the expansion trunks, which ensure that the 

 main tanks shall always remain full, and the coffer-dam, which isolates 

 the tanks from the machinery space. The expansion trunks extend 

 upwards from the tanks, like the neck of a bottle, and although of 



