Although chemistry had come a long way in the century that separated Newton and Boyle from Scheele and Priestley and Henry Cavendish, it still had a long way to go. Right up to the closing years of the eighteenth century (and in Priestley's case a little beyond) scientists everywhere searched for, and sometimes believed they had actually found, things that just weren't there: vitiated airs, dephlogisticated marine acids, phloxes, calxes, terraqueous exhalations, and, above all, phlogiston, the substance that was thought to be the active agent in combustion. Somewhere in all this, it was thought, there also resided a mysterious elan vital, the force that brought inanimate objects to life.

从牛顿和玻义耳，到金勒、普里斯特利和亨利·卡文迪许，中间隔着一个世纪。在这个世纪里，化学得到了长足的发展，但还有很长的路要走。直到18世纪的最后几年（就普里斯特利而言，还要晚一点），各地的科学家们还在寻找——有时候认为真的已经发现——完全不存在的东西：变质的气体、没有燃素的海洋酸、福禄考、氧化钙石灰、水陆气味，尤其是燃素。当时，燃素被认为是燃烧的原动力。他们认为，在这一切的中间，还存在一种神秘的生命力，即能赋予无生命物体生命的力。

No one knew where this ethereal essence lay, but two things seemed probable: that you could enliven it with a jolt of electricity (a notion Mary Shelley exploited to full effect in her novel Frankenstein ) and that it existed in some substances but not others, which is why we ended up with two branches of chemistry: organic (for those substances that were thought to have it) and inorganic (for those that did not).

谁也不知道这种难以捉摸的东西在哪里，但有两点是可信的：其一，你可以用电把它激活（玛丽·谢利在她的小说《弗兰肯斯泰因》里充分利用了这种认识）；其二，它存在于某种物质，而不存在于别的物质。这就是化学最后分成两大部分的原因：有机的（指被认为有那种东西的物质）和无机的（指被认为没有那种东西的物质）。