那时想把橡胶做得既硬又结实的尝试全失败了。

At that time every attempt to make rubber hard and strong came to nothing.

youdao

后来，他的一个朋友发现在橡胶里掺入硫磺，经过日晒，可以使橡胶变得又硬又结实。

Later, a friend of his had the idea that rubber might be made hard and strong if mixed with sulphur and put in the sun.

youdao

后来，他的一个朋友发现在橡胶里掺入硫磺，经过日晒，可以使橡胶变得又硬又结实。

Later, a friend of his had the idea that rubber might be made hard and strong if mixed with sulphur and put in the sun.

youdao