134 



SIR H. DAVY S AGRICULTURAL CHEMISTRY. 



tion different proportions of the same sub- 

 stances, water, carbonic acid, and car- 

 bon. 



The following specific grnvitics of the 

 different volatile oils were ascertained by 

 Dr. Lewis. 



Oil of Sassafras - - - 1094 

 Cinnamon ^ - - lo35 

 Cloves - - - 1034 



Fennel - - - 997 



Dill - - - - 994 

 Penny royal - - 97S 



Cummin - - _ 975 

 Mint - ... 975 

 Nutmegs - - - 948 

 Tansy - - ' - - 94G 

 Caraway - - _ 940 

 Criganum - - - 940 

 Spike - - - - 936 

 Rosemary ... 934 

 Juniper - - - 911 



Oranges - . - 888 

 Turpentine - - - 792 

 The peculiar odors of plants seem, in 

 almost all cases, to depend on the peculiar 

 volatile oils they contain. All the per- 

 fumed distilled waters owe their peculiar 

 properties to the volatile oils they hold 

 in solution. By collecting the aromatic 

 oils, the fragrance of flowers, so fugitive 

 in the common course of nature, is as it 

 were, embodied and made permanent. 



It cannot be doubted that the volatile 

 oils consist of carbon, hydrogen, and 

 oxygen ; but no accurate experiments 

 have as yet been made on the proportions 

 in which these elements are combined. 



The volatile oils have never been used 

 as articles of food; many of them are 

 employed in the arts, in the manufacture 

 of pigments and varnishes; but their most 

 extensive application is as perfumes. 



17. Woody fibre is procured from the 

 wood, bark, leaves, or flowers of trees by 

 exposing them to the repeated action of 

 boiling water and boiling alcohol. It is 

 the insoluble matter that remains, and is 

 the basis of the solid organized parts of 

 plants. There are as many varieties of 

 woody fibre as there are plants and organs 

 of plants; but they are all distinguished 

 by their fibrous texture, and their in- 

 solubility. 



Woody fibre burns with a yellow flame, 

 and produces water and carbonic acid in 



burning. When it is distilled in close 

 vessels, it yields a considerable residuum 

 of charcoal. It is from woody fibre, in- 

 deed, that charcoal is procured for the 

 purposes of life. 



The following table contains the results 

 of experiments made by Mr. Mushet, on 

 the quantity of charcoal afforded by the 

 different wood. 



100 parts of Lignum vitas 26.8 charcoal. 

 Mahogany 25.4 " 

 Laburnum 24.5 " 

 Chestnut 23.2 " 



Oak 22.6 " 



American black 



beech 21.4 " 



Walnut 20.60 " 



Holly 19.9 « 



Beech 19.9 " 



A meric. maple 19.9 " 

 Elm 19.5 " 



Norway pine 19.2 " 

 Sallow 18.4 « 



Ash 17.9 " 



Birch 17.4 " 



Scottish fir 16.4 " 

 MM. Gay Lussac and Thenard have 

 concluded from their experiments on the 

 wood of the oak and the beech, that 100 

 parts of the first contain : 

 Of Carbon - . . . 52.53 



Oxygen - - _ _ 41.78 

 Hydrogen - - - - 5.69 

 and 100 parts of the second : 

 Of Carbon - - . . 51.45 



Oxygen - - - - 42.73 

 Hydrogen - - - - 5.82 

 Supposing woody fibre to be a definite 

 compound these estimations lead to the 

 conclusion, that it consists of 5 propor- 

 tions of carbon, 3 of oxygen, and 6 of 

 hydrogen, or 57 carbon, 45 oxygen, and 

 6 hydrogen. 



It will be unnecessary to speak of the 

 applications of woody fibre. The dif- 

 ferent uses of the woods, cotton, the barks 

 of trees, are sufficiently known. Woody 

 fibre appears to be an indigestible sub- 

 stance. 



18, The acids found in the vegetable 

 kingdom are numerous ; the true vege- 

 table acids, which exist ready formed in 

 the juices or organs of plants, are the 

 oxalic, citric, tartaric, benzoic, acetic, 

 malic, galic, and prussic acid. 



