350 HISTORY OF SCIENCE. 



traverses the tube A, filled with chloride of calcium, by which it is 

 thoroughly dried. In the original form the experiment is open to the 

 objection that the water given off from the flame may have been simply 

 carried over by the stream of gas from the generating-bottle. c in the 

 figure is a cold dry glass bell-jar held over the flame. The water im- 

 mediately bedews the inner surface, and soon runs down in drops. 

 We shall presently see how Lavoisier accomplished the direct union 

 of oxygen and hydrogen gases in such a manner tha't the true com- 

 position of water was demonstrated beyond all cavil. 



At the end of 1781 an Englishman named WALTIRE exploded a 

 mixture of air and hydrogen by means of electric sparks, and he 

 noticed the deposition of moisture. In 1782 and 1783 Cavendish and 

 Priestley severally repeated these experiments, and Watt suggested 

 that they afforded indications that air was not an elementary body ; 

 but he put forward these views with hesitation, and even withdrew his 

 paper when a portion of it only had been read before the Royal 

 Society. We may see in Watt's diffidence how strongly the notion of 

 the elemental nature of air still possessed men's minds, when he feared 

 publicly to call it in question until he had conclusive experiments to 

 adduce in support of his own views. The phlogistic doctrine gave 

 such a form to the ideas of Cavendish, Priestley, and Watt, that they 

 failed to draw from the experiments with which they were acquainted 

 those conclusions which Lavoisier, who had liberated himself from the 

 illusory theory, about the same time, viz., 1783, clearly and definitely 

 enunciated. In fact, by the year 1784 Lavoisier had distinctly demon- 

 strated the composition of water, not only by producing the liquid from 

 its elements, but by the separation of these elements from the liquid. 

 The mode in which he arranged his experiments will be described 

 when we come to speak particularly of his labours. 



At the very period when the overthrow of the phlogiston theory was 

 approaching, several of the eminent chemists whose discoveries has- 

 tened its downfall were nevertheless its attached partisans, and still 

 strove to put the new wine into the old bottles. Sweden had by this 

 time become conspicuous by the distinguished cultivators of science 

 she fostered, and in the development of chemistry she seemed destined 

 to play a leading part. Two Swedish chemists of the epoch which now 

 occupies our attention must here be particularly mentioned. These 

 are Bergmann and Scheele. 



TORBERN BERGMANN (1735 1784) was born at Catherineberg, 

 where his father was collector of taxes. At seventeen years of age 

 Bergmann became a student at the University of Upsal, and there he 

 devoted himself with ardour to the study of mathematics and natural 

 science. At the age of twenty-six he was appointed to a professorship 

 of mathematics, but six years afterwards exchanged his chair for one 

 of chemistry and mineralogy, and in his new capacity he strove to 

 accomplish as much for chemistry as the great Linnaeus had done for 



