All my life through, the new sights of Nature made me rejoice like a child.

To every action there is always opposed an equal reaction； or， the mutual actions of two bodies upon each other are always equal， and directed to contrary parts.

质量是免费的。它不是礼物，但它是免费的。花钱的是那些不质量的东西——所有那些没有第一次就把工作做好的行为。