70 LIFE. 



microscope. The water appears as clear "and transparent 

 as the glass on which it rests. Both slides may now be 

 placed in a warm room under the same conditions for a few 

 hours, taking care that light and air have free access to both 

 specimens, and that any fluid lost by evaporation be sup- 

 plied. At the end of five or six hours the slides may again 

 be examined. 



The one containing the inorganic deposit of phosphate 

 of lime shall be called A. No change has taken place. 

 There are the little lifeless particles still moving as before 

 in the fluid in which they are suspended. Some of them 

 indeed may have become aggregated together so as to form 

 little collections, but beyond this there appears to have been 

 no change. 



Next let the other slide B be examined. The fluid which, 

 when first seen, was perfectly clear, now contains a number 

 of exceedingly minute dots, points, or granules, closely 

 resembling those of the phosphate of lime, and these mani- 

 fest similar molecular movements. If a little gum, glycerine, 

 or any viscid material be added to the particles on each 

 slide, the molecular movements are immediately suspended, 

 and if the fluid be diluted they recur. This indicates that 

 in both cases the movements are due to physical causes. 

 The little particles which could move freely in such a limpid 

 fluid as water, are prevented from moving if the fluid in 

 which they are suspended be rendered viscid. 



Let both slides be again set aside for a few hours longer. 

 It will be found that the inorganic matter upon the slide A 

 has undergone no change. But the case is very different 

 with regard to B. The granules that have appeared in the 



