19．When you think about inventions that have changed human's lives，what comes to mind？The car．the compass （指南针） or the computer？We hardly think about those more common things．But without them，our life will be much worse，for example，eyeglasses．Imagine a world without glasses，many of us would walk into things．So who invented glasses，and how were they first made？
The truth is that nobody knows who invented eyeglasses．What we do know is that the earliest lenses （镜片）made from quartz （石英）．As soon as people worked out how to make glass without bubbles they started miking lenses out of glass．
Glasses spread quickly all over Europe and Asia．But early glasses were squeezed （夹） onto the bridge of the nose．It was painful for the wearers．So there was still one big problem：
How to keep them on the wearer's face．It took nearly 400years for people to come up with the way wear glasses today
We should be thankful lo Benjamin Franklin，who invented bifocals（双焦点眼镜） in the1780s．He liked lo read or watch sceneries（景色） far away while traveling．But he hated to change glasses all the time．Then Franklin cut his glasses in half and put them together with his distance glasses．Now they are still popular．
76．Which invention is more common，the compass or the glasses？The glasses．
77．What were the earliest lenses made from？They were made from quartz．
78．Where were glasses popular after they were invented？All over Europe and Asia．
79．How long did it take people to think of the way we wear glasses today？Nearly 400 years．
80．When were the bifocals invented？In the 1780s．．
