IX THE LAST HALF-CENTURY. 43 



sisted of minute indivisible particles or 

 atoms, separated by a universal vacuum ; 

 according to the other, it was continuous, 

 and the finest distinguishable, or imagina- 

 ble, particles were scattered through the 

 attenuated general substance of the ple- 

 num. A rough analogy to the latter case 

 would be afforded by granules of ice dif- 

 fused through water ; to the former, such 

 granules diffused through absolutely emp- 

 ty space. 



In the latter part of the eighteenth 

 century, the chemists had arrived at sev- 

 eral very important generalisations re- 

 specting those properties of matter with 

 which they were especially concerned. 

 However plainly ponderable matter 

 seemed to be originated and destroyed in 

 their operations, they proved that, as 

 mass or body, it remained indestructible 

 and ingenerable ; and that, so far, it va- 

 ried only in its perceptibility by our 

 senses. The course of investigation fur- 



