MATTER 23 



gas; or that by uniting sulphur and carbon, two 

 solids, we would obtain a very volatile liquid of an 

 extremely unpleasant odor; or, again, that by the 

 union of one volume each of nitrogen and chlorine 

 together with four volumes of hydrogen — all three of 

 them gases — we would obtain a white solid, known as 

 chloride of ammonium. 



Examples might be multiplied indefinitely, but 

 these few are sufficient to show how widely different 

 are the properties of compounds from the proper- 

 ties of their constituent elements. 



All material thing3 with which we are acquainted, 

 the thousands of different objects upon the earth, are 

 built of a few primary building materials. 



As infinite varieties of houses may be built of stone, 

 and brick, and mortar, so countless varieties of com- 

 pounds may be built of atoms of a few different 

 kinds. The same atom may be made to do many 

 different kinds of service. It is indeed an amazing 

 fact that the primary building materials of the 

 earth and of the other worlds which have revealed 

 thier composition, at least partly, through the spec- 

 troscope, are but a few kinds of atoms, and that 

 these atoms are inconceivably small. 



And yet each atom is subject to definite and invari- 

 able laws. The laws of the material universe are the 

 laws of atoms. Atoms are the law-abiding citizens 

 of the universe; they do their work with absolute 

 precision. The fundamental laws of chemistry are 

 mathematically exact. 



For example, take the law of " definite propor- 

 tions," that in every chemical compound the. kinds 

 and relative quantities of the constituent elements 

 are fixed and invariable. One correct analysis of 

 pure water determines the composition of all water 

 in existence. The chemist cannot believe that the 



