as it is when the servant puts coals on and lights the fire: the substances wait until we do something which is able to start the action. Can anything be more beautiful than this combustion of charcoal in oxygen? You must understand that each of these little sparks is a portion of the charcoal, or the bark of the charcoal, thrown off white-hot into the ogygen, and burning in it most brilliantly, as you see. And now let me tell you another thing, or you will go away with a very imperfect notion of the powers and effects of this affinity. There you see some charcoal burning in oxygen. Well, a piece of lead will burn in oxygen just as well as the charcoal does, or indeed better; for absolutely that piece of lead will act at once upon the oxygen as the copper did in the other vessel with regard to the chlorine. And here also a piece of iron: if I light it and put it into the oxygen, it will burn away just as the carbon did. And I will take some lead, and shew you that it will burn in the common atmospheric oxygen at the ordinary temperature. These are the lumps of lead which, you remember, we had the other day—the two pieces which clung
