C 243 J 



mical changes before they can become the food of 

 plants. 



It will be proper to take a scientific -view of the 

 nature of these changes ; of the causes which occasion 

 them, and which accelerate or retard them ; and of 

 the products they afford. 



If any fresh vegetable matter which contains su- 

 *gar, mucilage, starch, or other of the vegetable com- 

 pounds soluble in water be moistened and exposed to 

 air, at a temperature from 55 to SO , oxygene will 

 soon be absorbed, and carbonic acid formed ; heat 

 ..will be produced, and elastic fluids, principally car- 

 bonic acid, gaseous oxide of carbon, and hydro- car- 

 bonate will be evolved ; a dark coloured liquid of a 

 slightly sour or bitter taste will likewise be formed ; 

 and if the process be suffered to continue for a time 

 sufficiently long, nothing solid will remain, except 

 earthy and saline matter, coloured black by charcoal. 



The dark coloured fluid formed in the fermenta- 

 tion always contains acetic acid ; and when albumen 

 or gluten exists in the vegetable substance, it likewise 

 contains volatile alkali. 



In proportion as there is more gluten, albumen, 

 or matters soluble in water in the vegetable substances 

 exposed to fermentation, so in proportion, all other 

 circumstances being equal, will the process be more 

 rapid. Pure woody fibre alone undergoes a change 

 very slowly ; but its texture is broken down, and it is 

 easily resolved into new elements when mixed with 

 substances more liable to change, containing more 

 oxygene and hydrogene. Volatile and fixed oils, resins 



