8oz THE POPULAR SCIENCE MONTHLY. 



have raised chemistry to its present important position, together 

 with the insight into the manifold changes and metamorphoses 

 which terrestrial matter has undergone in past times, and which 

 it still undergoes, and into the processes active in vegetable and 

 animal organisms. 



The events preceding the discovery of the composition of water 

 afford a striking instance of how many difficulties had to be over- 

 come from the very first observations on the chemical nature of 

 this body — ubiquitous on the surface of the earth — to the ascer- 

 tainment of its composition, and to our ability voluntarily to pre- 

 pare it. In the middle ages the doctrine of Aristotle was pre- 

 dominant, that all matter consisted of four elements — air, fire, 

 earth, and water — difference in properties being ascribed only to 

 the varying proportions in which these elements were present. 

 Not much more was known of its physical and chemical characters, 

 but that it may be brought into a solid state by cold and volatil- 

 ized by heat, and that it offers a good solvent for many substances. 

 Paracelsus, a prominent physician and chemist of the sixteenth 

 century, found that, on treating iron with sulphuric acid, a gas is 

 given off. Boyle, in 1672, discovered this gas to be inflammable ; 

 thirty years later, its detonating properties in contact with air 

 became known ; but not until Cavendish, in 1766, devoted himself 

 to the exact study of this gas was there any conjecture established 

 on the relations existing between it and water. In 1787 Cavendish 

 made the discovery that, by combustion of this gas in air, water is 

 generated ; but, prejudiced by the chemical theories then prevail- 

 ing, he failed to explain the process in the right way. We are 

 indebted to Lavoisier for a correct definition of the changes taking 

 place in the combustion of hydrogen, which name he gave to the 

 gas in question, signifying a body from which water may be gen- 

 erated by uniting it with oxygen. Thus Lavoisier, supported by 

 the discovery of oxygen by Priestley and Scheele in 1774, became 

 the originator of chemical synthesis. It is a trifling experiment 

 nowadays to demonstrate the formation of water by placing an 

 inverted glass over a jet of burning dry hydrogen, when a dew of 

 water will cover the sides of the vessel and gradually gather into 

 drops. 



A rapid advance in synthetical knowledge took place during 

 the third and fourth decades of this century, the artificial prepa- 

 ration of a long series of organic compounds becoming known ; 

 and it is a surprising fact, although the chemistry of the carbon 

 compounds, or organic chemistry, was in an infantile state at that 

 time, while most mineral bodies were pretty well known as to 

 their composition and character, that the manufacturing of the 

 former with all their physical and chemical properties was suc- 

 cessfully performed, while the imitation of minerals in their 



