1 1 2 On tfie Decomposition and Composition of the Alkalis. 



voured to show*, may contain both saline and metallic im- 

 pregnations ; and the free atmosphere almost constantly 

 holds in mechanical suspension solid substances of various 

 kinds. . . , 



•. 'In,the.;common processes .of Nature, all the- products of 

 living beings may be easily conceived to be elicited from 

 know.n combinations of matter. The compounds of iron, of 

 the alkalis, and earths, with mineral acids, generally abound 

 in soils. From the decomposition of basaltic, porphyrinic f , 

 and granitic rocks, there is a constant supply of earthy al- 

 kaline and ferruginous materials to the surface of the earth. 

 In the sap of all plants that have been examined, certain 

 neutrosaljne compounds, containing potash, or soda, or 

 iron, have been found. From plants they may be supplied 

 to animals. And the chemical tendency of organization 

 seems to be rather to combine substances into more compli- 

 cated and diversified arrangements, than to reduce them into 

 simple elements. 



case of vegetation in which the free atmosphere was excluded, the seeds grew 

 in white sand, which is stated to have been purified by washing in muriatic 

 acid; but such a process was insufficient to deprive it of substances which 

 might afford carbon, or various inflammable matters. Carbonaceous matter 

 exists in several stones which afford a whitish or grayish powder ; and when. 

 in a stone the quantity of carbonate of lime is very small in proportion to 

 the other earthy ingredients, it is scarcely acted oh by acids. 



* Bakerian Lecture, 1806, page 8. 



f In the year 1804, for a particular purpose of geological incjuiry, I made 

 an analysis of the porcelain clay of St. Stevens, in Cornwall, which results 

 from the decomposition of the feldspar of finegrained granite. I could not 

 detect in it the smallest quantity of alkali. In- making some experiments on 

 specimens of the undecompounded rock taken from beneath the surface, 

 there were evident indications of the presence of a fixed alkali, which seemed 

 to be potash. So that it is very probable that the decomposition depends on 

 the operation of water and the carbonic acid of the atmosphere on the alkali 

 forming a constituent part of the crystalline matter of the feldspar, which 

 Hiay disintegrate from being deprived of it. 



[To be continued.] 



XVIII. An 



