364 HISTORY OF SCIENCE. 



and when twenty-one years old he gained a prize offered by the Govern- 

 ment for the best essay on the most effectual means of lighting the 

 streets of Paris. When twenty-five years of age he was admitted to 

 the Academy of Sciences, and he would probably have devoted his 

 splendid abilities to mathematics had the brilliant discoveries of Black 

 (page 344) not determined his choice to chemistry. He published a 

 series of essays in 1772 giving an historical review of the progress of 

 the science, and in the last one defending the teaching of Black regard- 

 ing fixed air. He soon perceived that Stahl's phlogistic theory gave 

 an insufficient and inconsistent explanation of chemical phenomena, 

 and he devoted great attention to the elaboration of some more satis- 

 factory doctrine. He began by carefully repeating the experiments of 

 Black, Priestley, Scheele, and others, and contrived various ingenious 

 arrangements by which he could make quantitative estimates of the 

 substances he used, and the gaseous and other products he obtained. 

 Except the volume of essays mentioned above, all Lavoisier's scientific 

 papers were published in the Memoires of the Academy of Sciences. 

 In 1789 he published a work in which his own investigations and con- 

 clusions were embodied in a systematic manner, and these may be 

 said to have included in some form the latest discoveries of that time. 

 Lavoisier's work effected a revolution in chemical science relatively 

 greater than that great convulsion through which France was then 

 passing effected in the political world. Sad to say, the brilliant chemist 

 was himself a victim of that terrible period. When the sanguinary 

 Robespierre was in power, Lavoisier was accused of having defrauded 

 the revenue, of which he had been a receiver. He was thrown into 

 prison, and on the 8th of May, 1794, was led to the guillotine, in the 

 fifty-first year of his age. 



The closeness of the reasoning in which Lavoisier discusses his 

 experiments ; the accuracy, neatness, and elegance, so to speak, of the 

 experiments themselves, have never been excelled. He, if any one, 

 is the founder of modern chemistry, and the science of to-day bears 

 the impress of his hand. The overthrow of the phlogistic theory which 

 he effected; his demonstration of the part played by oxygen; his 

 investigations on the composition of water and of the atmosphere ; and 

 his views on the composition of oxides, acids, and salts, are the chief 

 subjects which we shall discuss in the present chapter. 



He took a retort with a long neck, and having bent the neck as in 

 Fig. 174, filled the vessel A with quicksilver, and placed it en a furnace, 

 B, as shown in the figure, so that the end of the neck E passed into 

 the inside of a bell jar, which stood inverted in a vessel of mercury, 

 M. The quantity of air within the bell jar was so adjusted that the 

 quicksilver stood at the same level within and without the jar, and 

 this height was carefully marked by pasting a slip of paper on the 

 jar. A fire was then lit in the furnace B, and kept up continually 

 for twelve days, so as to keep the quicksilver in the retort A always 



