Of TH£ ASU Of PLANTS. 23 



by burning a common locofoco match : the white 

 smoke which goes off at first before the sulphur ig- 

 nites, is phosphoric acid. Phosphorus is used in the 

 making of these matches, because it is a substance that 

 inflames easily by a little friction. All who have rub- 

 bed them on a wall or board in the dark, have oljserved 

 that they leave a qui' istinctlv 



visible. If the mat. i it will 



also appear bright, and the peculiar smell of phos- 

 phorus may be perceived. • 



Phosphoric acid does not seem to exist in so large 

 quantity as sulphuric acid, as it does not constitute a 

 principal portion of any of our rocks. It forms a very 

 important part of the bones of animals. 



n. DVnEKHCBB m THB A8B or CULTITATKD 

 PLAMTS. 



We have now noticed each of the substances that 

 were named as occurring in the inorganic part of 

 \y of their more remarkable 



jii >n forms of appearance as 



•eetaed uccessary to their recognition by the practical 

 man. 



It has been already stated, that with one or two 

 o'' '-"'""al exceptions, they are all fouinl in the ash of 



< I plants. Sometimes one and sometimes an- 

 ( it, but gtii. " • find small quantities 



< It does : .V frotn thU. however, 

 V plant contains tlu- sainr n of ash. 



i k of a tree, for instiuioe, i: _ td of its 



bark, does not yield more than from one to two {loimds 

 of ash in one hundrwi of wood, while the stalk of grass 

 or straw of i^rain Inijuently contains from 6 to 14 lbs. 



in 100. There are some plants which ^< '" ' on- 



tain any a.sh whatever, and others in whi us a 



large proportion. This difference exists nut only be- 



