Which cargo can be carried on an exposed deck?

What cargo might be carried openly on an early twentieth-century cargo ship?

The tentative examples are relatively light bulk materials such as wood and canvas that tolerate exposure to salt spray.

Resistance to salt spray, rust, and decay is the starting point for considering exposed deck cargo. Wood and canvas are tentative examples of relatively light bulk items. Dense cargo presents a different problem even if the material itself resists corrosion, while cars are suggested for stowage below. These are exploratory suggestions rather than a particular ship's cargo plan.