LECTURE II.] HISTORY OF CHEMISTRY. 23 



very few chemists. At a later date Lavoisier expresses himself 

 still more distinctly, stating that the substances employed and 

 the products obtained can be brought into an algebraical equa- 

 tion ; and that if any term is unknown it can be calculated. 16 

 This is the first idea of those equations which we now employ 

 daily. 



Still we do not foresee the course of the development of this 

 great thinker's ideas, if we follow him, in a general way at 

 least, from his first experiments onwards. It may be said, how- 

 ever, that the development of his views is that of the chemistry 

 of his period. 



One of Lavoisier's earliest investigations deals with the 

 supposed conversion of water into earth. 17 He points out the 

 inaccuracy of this supposition, which was generally held at the 

 time. It is interesting to follow him in his experiments. He 

 seals up a quantity of water in a glass vessel, which was known 

 at that time as a pelican, and is so arranged that a glass tube 

 which is fused on to its neck above, leads the condensed water 

 back again into the body of the vessel. He weighs this empty, 

 and then with water in it, after closing the single opening by 

 means of a glass stopper. He then distils the water for a 

 hundred days. The formation of earth appears after a month, 

 but he proceeds with the distillation until the quantity formed 

 seems to be sufficient. He now weighs the apparatus again, 

 and finds it to be just as heavy as before ; whence he concludes 

 that no fire material has penetrated it ; for otherwise, he con- 

 siders that the weight must have been increased. He next 

 opens it, weighs the water along with the earth, and finds its 

 weight increased, but that of the glass diminished. This leads 

 him to the assumption that the glass has been attacked by the 

 water, and that the formation of earth is not a conversion but 

 a decomposition. His conclusions accord exactly with his ex- 

 periments ; yet he does not permit himself to be blindly led 

 by them. Thus he finds the increase in the weight of the 

 water to be a few grains more than the decrease in the weight 



16 Dumas, Le9ons. 157. 17 Lavoisier, Oeuvres. 2, I. 



