Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.
毫无疑问，每增加一点知识，你就会忘记一些你以前知道的东西。因此，最重要的是不要让无用的事实排挤掉有用的事实。