56 PROCEEDINGS OF THE INDIANA ACADEMY OF SCIENCE. 



In 1807, a most imi)ortant discovery was made by Sir Humplirey Davy. 

 He applied his galvanic battery to the decomposition of caustic soda and 

 caustic potash. This lead to decomposing calcium chloride and other related 

 compounds, and finally to the ]ireparation of the metal aluminum by Wohler 

 in 1S27 from certain compounds of potassium and clay. Davy also proved 

 that oxygen is not a necessary constituent of an acid, but that hydrogen is. 

 A number of theories and laws soon followed. Dalton established the laws of 

 definite and inultiple proportions and the atomic theory. Gay-Lussac's law of 

 combining gases and Avogadro's law were important discoveries. 



The work of Berzelius followed in determining the atomic weights which 

 developed most of our analytic methods. He closed his work in 1848. 



The law of specific heat was discovered by Dulong and Petit in 1819. 

 The work of these men lead to a much clearer knowledge of the molecule and 

 the atom with its electrons and the nature and composition of gases, together 

 with the powers of combination. In organic chemistry especially the study 

 of the structure of chemical compounds has resulted in great progress in the 

 industrial world, for it was discovered that new compounds could be made by 

 uniting the elements composing them, such as urea, uric acid, caffeine, 

 alizarine, indigo and some alkaloids. This method of building compounds 

 has led to the manufacture of gun-cotton, dynamite, and similar explosives, 

 the development of the candle industry, to the impro\ement of tanning and 

 brewing and the preparation of gases and oils aiul nuiny other lines of industry. 



The periodic system or the arrangement of the elenu'iits according to their 

 atomic weights is one of the greatest generalizations of the century. This 

 has been developed by Xewland beginning in 18(i4, and Meyer, followed by 

 Mendeleef in 18(W and others continuing the study. 



Thus chemical thought has continually advanced through the century 

 and the result has been the marvelous application to almost everything: 

 agriculture, manufacturing, mining, in the home, in business, in medicin(^s and 

 in the arts. 



III. Physics. 



The advances made in physics are as surprising as in ol her lines of scientific 

 thought. The century opened with conceptions that could not stand the test 

 of modern methods of thinking and experimenting. 



For instance, the caloric theory of heat that held that heat was a subtile 

 fluid had just been exploded by Count Kumford who showed that heat is the 

 result of molecular motion. Newton's corjjuscular theory of light was still 

 generally accepted. Fhen in the eighth edition of the encyclopedia Brit- 

 tannica published in 1856, heat was defined as a material agent of a peculiar 

 nature, highly attenuated. 



Fourier demonstrated the laws of conduction by mathematical as well as 

 by physical research which also covers elcclrical conduction and this is the 

 real basis of Ohm's Law. 



