PART IV. AGRICULTURE. 191 



sign that they overflow their banks. The presence of the as- 

 phodelus palustris is generally a certain indication that the dro- 

 sera is near, which brings on a terrible disease in cattle, and 

 often turns their milk into blood in mossy soils. The water- 

 lily in pools among moss or peat commonly indicates marl, or 

 rich clay, &c. The different species of lichens upon stones 

 indicate their firm close texture ; the bryums and jmigermaniums 

 generally the contrary. The absence of all moss on stones 

 exposed to the weather, shews that they are oxydable, that 

 their surface crumbles off in the winter season, and consequently 

 that they are unfit for being used in buildings. 



4. The Uses of Vegetables. — These are either for supporting 

 life, restoring health, furnishing food for animals, or being used 

 in the arts. With respect to medical and nutritive qualities, 

 that knowledge is acquired either by observing the daily food of 

 cattle; or the instinct of these or other inferior animals, which 

 often, when diseased, have recourse to certain plants that give 

 them relief — hence the names of dog-grass, cat-mint, &c. ; or 

 by observing what effect is produced upon cattle by pastures in 

 which particular plants prevail. In this manner Linnaeus ob- 

 served what took place after harvest when cows were turned 

 upon the stubbles ; and this fact is taken advantage of by such 

 as give parsley, mint, &c. to their cows on certain occasions; or 

 it may be also derived from actual experiment upon animals, 



