In fifty years there'll be twenty people per square yard, it is written here.
这里写着,再过五十年每平方码将要住着20人的人口密度。
It was the idea of supporting a craft on a 'pad',or cushion, of low-pressure air, ringed with a curtain of higher pressure air.
用一个气垫来支撑船体,低压空或软垫,软垫周围用高压空气环绕。