216 Progressive Changes of Matter. [Oct., 



stance from other sources. It is but a concentration of invisible 

 particles by which a visible and tangible body exists, as an illus- 

 tration by which unseen elements are brought into visible forms. 

 Salt dissolved in water ceases to be visible, no trace of its el- 

 ements or parts can be detected by the eye. But by evaporating 

 the water, its presence becomes apparent. Hence we learn that 

 water is the solvent of saline substances. By evaporation water 

 is dissipated in air, and after ascending to certain heights, it is 

 condensed into drops and falls upon the earth. Here m'c also 

 learn- that the atmosphere is the solvent of water. From the above 

 illustrations it will be no difficult task to conceive of the trans- 

 mutation of things from one form to another. Hence we are to 

 infer that the constituent parts of a tree are principally contained 

 in the atmosphere. The science of chemistry and botany have 

 brought to light, in a measure, the manner in which these elemen- 

 tary substances are accumulated in the formation of a tree. A 

 casual observer cannot fail to notice, that the woody part of a tree 

 is made up of concentric rings, that each ring is formed during 

 the existence of the leaves of the tree, and its years by the num- 

 ber of these rings may be accurately ascertained. This growth 

 or formation of the tree has but two simple processes, through 

 the medium of the roots and leaves. The roots have their spon- 

 gioles, through which a fluid passes up the tree from the ground 

 to the leaf. The leal also contains its orifices or inhaling organs 

 by which another substance is imbibed; these two substances 

 combined, pass down the tree between the bark and woody por- 

 tion, leaving a deposit in their descent, forming through the pro- 

 cess of drying, the bark and woody fibre. We can therefore have 

 a clear and well defined idea of the manner in which a tree ob- 

 tains its growth. Hence we infer that the constituent parts of a 

 tree once existed in a fluid form and in other localities. Now 

 what we affirm of one tree we may aihrm of all trees, of all veg- 

 etable bodies that exist in the atmosphere, and we can thereby 

 escape all confusion of ideas in obtaining a knowledge of the 

 growth of a forest of trees, however extensive. 



In the formation of a river there is likewise one uniform pro- 



