 However, by the end of the 1770s, Torbern Olaf Bergman (1735–1784) made a series of careful measurements of the weights of metals and their calxes. He showed that the calcination of metals led to a gain in their weight equal to the weight of oxygen lost by the surrounding air. This ruled out the two explanations given above, but interestingly, he took this in his stride, arguing that, as metals were being transformed into their calxes, they lost weightless phlogiston. This phlogiston combines with the air’s oxygen to form ponderable warmth, which in turn combines with what remains of the metal after loss of phlogiston to form the calx. Lavoisier simplified this explanation by removing the phlogiston from this scheme. This moment is what many call the Chemical Revolution.