German inventor Anton Flettner patented the idea of a rotor sail in 1922. A new improved version is back (”These 150-foot-high sails could help solve shipping’s climate problem,” Online, April 22).

Crave freelancer Tim Hornyak is the author of "Loving the Machine: The Art and Science of Japanese Robots." He has been writing about Japanese culture and technology for a decade. E-mail Tim. Many ...