THE STONE SKELETON OF THE SCOURING-RUSH I I I 



is, in fact, as much a mineral as a vegetable tube that 

 we have here, as may be shown by a very pretty chem- 

 ical experiment. 



If we take a small vial of nitric acid and immerse any 

 ordinary leaf therein, we shall quickly see it dissolve 

 literally eaten up by the acid. But what does the 

 scouring-grass do under such treatment? Immediately 

 upon its introduction to the acid the sizzling process 

 begins ; the green pulp of the stem is gradually con- 

 sumed, the tube, however, still retaining its shape, be- 

 coming paler and paler in color, until, after a few hours, 

 our specimen is transformed into a pure white alabas- 

 ter-like column, which defies any further attack from 

 the acid. Upon taking it from the vial and washing it 

 carefully in running water we hold in our hands a beau- 

 tiful tube of pure glassy flint or silex, and an object of 

 great microscopic beauty of construction. Our scour- 

 ing-rush is no longer a vegetable, but a mineral, and, 

 in its skeleton of stone, we easily understand the secret 

 of its utility as a scouring -brush. 



