6 PRINCIPLES OF CHEMISTRY 



increase in mass of itself and from itself, but it grows because it absorbs 

 gases from the atmosphere and sucks water and substances dissolved 

 therein from the earth through its roots. The sap and solid substances 

 which give plants their form are produced from these absorbed gases 

 and liquids by complicated chemical processes. The gases and liquids 

 are converted into solid substances by the plants themselves. Plants 

 not only do not increase in size, but die, in a gas which does not contain 

 the constituents of air. When moist substances dry they decrease in 

 weight ; when water evaporates we know that it does riot disappear, 

 but will return from the atmosphere as rain, dew, and snow. When 

 water is absorbed by the earth, it does not disappear there for ever, but 

 accumulates somewhere underground, from whence it afterwards flows 

 forth as a spring. Thus matter does not disappear and is not created, 

 but only undergoes various physical and chemical transformations that 

 is to say, changes its locality and form. Matter remains on the earth 

 in the same quantity as before ; in a word it is, as far as we are con- 

 cerned, everlasting. It was difficult to submit this simple and primary 

 truth of chemistry to investigation, but when once made clear it rapidly 

 spread, and now seems as natural and simple as many truths which 

 have been acknowledged for ages. Mario tte and other savants of the 

 seventeenth century already suspected the existence of the law of the 

 indestructibility of matter, but they made no efforts to express it or to 

 apply it to the ends of science. The experiments by means of which 

 this simple law was arrived at were made during the latter half of the 

 last century by the founder of contemporary chemistry, LAVOISIER, the 

 French Academician and mayor. The numerous experiments of this 

 savant were conducted with the aid of the balance, which is the only 

 means of directly and accurately determining the quantity of matter. 



Lavoisier found, by weighing all the substances, and even the 

 apparatus, used in every experiment, and then weighing the substances 

 obtained after the chemical change, that the sum of the weights of the 

 substances formed was always equal to the sum of the weights of the 

 substances taken ; or, in other words : MATTER is NOT CREATED AND 

 DOES NOT DISAPPEAR, or that, matter is everlastiny. This expression 

 naturally includes a hypothesis, but our only aim in using it is to con- 

 cisely express the following lengthy period That in all experiments, 

 and in all the investigated phenomena of nature, it has never been 

 observed that the weight of the substances formed was less or greater 

 (as far as accuracy of weighing permits) than the weight of the sub-, 

 stances originally taken, and as weight is proportional to mass 11 or 



11 The idea of the mass of matter was first shaped into an exact form by Galileo (died 

 1642), and more especially by Newton (born 1643, died 1727), in the glorious epoch of the 



