136 CHYMISTRY APPLIED TO AGRICULTURE. 



is sometimes prescribed in medicine as a mild, soothing, 

 and easily digested article of nourishment. 



The use of gum in the arts is very extensive : it is used 

 in preparing cloths and felt for receiving a gloss ; writing- 

 paper is covered with a thin coating of it to prevent the 

 ink from spreading. Gum is used as a receiver of the 

 colors, which are applied by impression to cloths of all 

 kinds : the use of it in stamping cotton and linen goods is 

 now superseded in England by that of mucilage extracted 

 from lichens. 



The specific gravity of the gums is from 1300 to 1490, 

 water being 1000. Messrs. Gay-Lussac and Thenard found 

 gum Arabic to contain 



Carbon 42.23 



Oxygen 50.84 



Hydrogen 6.93 



Oxygen and hydrogen are found in it in the proportions 

 necessary for forming water. 



ARTICLE II. 



Starch or Fecula. 



Starch is a white, finely divided, pulverulent. substance, 

 insoluble in cold water, and forming a glue in boiling 

 water. When this substance is obtained from any other 

 plant than one of the grains, as from potatoes, corn-flag, 

 bryony, horse-chestnut, male orchis, dog-bane, burdock, 

 iris, hen-bane, patience, ranunculus, &/C., it is known by 

 the name of fecula. 



In many parts of America the principal food of the 

 inhabitants is procured from the fecula of the manioc. 

 The preparation of sago from the pith of old palm trees, 

 and of salep from the bulbs of all the varieties of orchis, 

 shows the important purposes which may be answered by 

 the fecula of various plants, in the arts, in medicine, and 

 as nourishment for the human species and for animals. 

 The fecula contained in all the plants I have just named 

 is wholesome, and very nourishing, and may be used as 

 food in various forms ; but it is necessary to keep in mind, 

 that in most of these vegetables it is combined with other 



