Dec. 1, 1864.] THE TECHNOLOGIST. 



AND THE FORMATION OF MAPLE SUGAR. 231 



circulation of the sap is up through the wood, and down through the 

 bark. 



There has been much speculation in relation to the force that causes 

 the sap of plants to circulate, but it has never been settled by observa- 

 tion and experiment. It is pretty well established that sap circulates in 

 the winter, though less rapidly than in the summer, and less rapidly at 

 that time in deciduous than in evergreen trees. 



The solid portions of thoroughly dried wood, and other parts of 

 plants, are composed mainly of water and charcoal. When charcoal is 

 burned, a small portion of ash is left. This ash is the mineral or in- 

 organic portion of the substance of the tree, and consists principally of 

 potash, lime, and flint or silex. That portion which burns is carbon. 

 In burning, the carbon unites with oxygen to form carbonic acid, an 

 invisible gas that floats away in the atmosphere. 



The water and the inorganic matters enter the tree through the 

 roots ; the carbon enters mostly through the leaves. Carbon forms about 

 one-half of the solid substance of the tree, and water the other half. 



Water is composed of two elements, oxygen and hydrogen, in the 

 proportion of eight pounds of oxygen to one of hydrogen. These in 

 entering into a chemical combination with carbon, lose the liquid state 

 of water, and form the various solid substances which make up the 

 body of the tree. 



In its course the sap undergoes important transformations. The 

 trunks and leaves of trees are scenes of constant chemical operations, 

 many of them more mysterious than any of the operations of the 

 laboratory. One of these is the decomposition of carbonic acid in the leaf. 

 The affinity of carbon and oxygen is very strong indeed, and there are 

 few forces in Nature that can rend these two elements asunder ; but the 

 combined action of light and vegetable life is separating them through- 

 out every day in the leaves of all growing plants. Carbonic acid is 

 absorbed from the atmosphere by the leaf, its two elements are torn 

 apart, the oxygen is returned to the air, and the carbon combining 

 chemically with other elements in the sap is carried to the places where 

 new wood is being formed, and is there deposited in its proper place to 

 help build up the structure of the tree. The symmetrical order in 

 which the carbon is deposited in a tree may be seen by looking at a piece 

 of charcoal. 



If wood is examined under a powerful microscope, it is found that 

 the tubes through which the sap circulates are formed of minute sacs 

 or cells. The substance of which the walls of these cells are formed is 

 called cellulose. It has been the subject of a great deal of chemical 

 research, and is found to consist of carbon and water, or more strictly, of 

 carbon and the elements of water, oxygen and hydrogen. Cotton and 

 linen are almost pure cellulose. Each atom of cellulose contains twelve 

 atoms of carbon, ten atoms of hydrogen, and ten of oxygen, C 13 H, O 10 . 

 Starch, gum, and sugar all have the same composition, C 12 H 10 O 10 . 



