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M. M. Gay Lussac and Thenard have deduced 

 three propositions, which they have called laws from 

 their experiments on vegetable substances. The first 

 is, " that a vegetable substance is always acid when- 

 ever the oxygene it contains is to the hydrogene in a 

 greater proportion than in water." 



The second, " that a vegetable substance is always 

 resinous or oily or spirituous whenever it contains 

 oxygene in a smaller proportion to the hydrogene than 

 4 exists in water." 



The third, " that a vegetable substance is neither 

 acid nor resinous ; but is either saccharine or mucila- 

 ginous, or analogous to woody fibre or starch, when- 

 ever the oxygene and hydrogene in it are in the same 

 proportions as in water." 



New experiments upon other vegetable sub- 

 stances, besides those examined by M. M. Gay Lussac 

 and Thenard, are required before these interesting 

 conclusions can be fully admitted. Their researches 

 establish, however, the close analogy between several 

 vegetable compounds differing in their sensible quali- 

 ties, and combined with those of other chemists, offer 

 simple explanations of several processes in nature and 

 art, by which different vegetable substances are con^ 

 verted into each other, or changed into new com- 

 pounds. 



Gum and sugar afford nearly the same elements 

 by analysis : and starch differs from them only in con- 

 taining a little more carbon. The peculiar properties 

 of gum and sugar must depend chiefly upon the dif- 

 ferent arrangement, or degree of condensation of their 



