Lead Balloon

摘要

I enjoyed Paul Collins's article on metal balloons down the ages (10 January, p 44). I am not sure, however, about his remark that, since 1941, "no more metal-clads have taken to the skies".rnI seem to recall reading, 30 or 40 years ago, of a successful project at the Massachusetts Institute of Technology to design, build and fly a balloon constructed entirely of lead.